Diffractive optical elements with optical power

ABSTRACT

A head mounted display system can include a camera, at least one waveguide, at least one coupling optical element that is configured such that light is coupled into said waveguide and guided therein, and at least one out-coupling element. The at least one out-coupling element can be configured to couple light that is guided within said waveguide out of said waveguide and direct said light to said camera. The at least one coupling element may comprise a diffractive optical element having optical power.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application No. 62/737,042, filed on Sep. 26, 2018,entitled “DIFFRACTIVE OPTICAL ELEMENTS WITH OPTICAL POWER,” which ishereby incorporated by reference herein in its entirety.

BACKGROUND Field

The present disclosure relates to optical devices, including augmentedreality imaging and visualization systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1 , an augmented reality scene 10 is depicted. Theuser of an AR technology sees a real-world park-like setting 20featuring people, trees, buildings in the background, and a concreteplatform 30. The user also perceives that he/she “sees” “virtualcontent” such as a robot statue 40 standing upon the real-world platform30, and a flying cartoon-like avatar character 50 which seems to be apersonification of a bumble bee. These elements 50, 40 are “virtual” inthat they do not exist in the real world. Because the human visualperception system is complex, it is challenging to produce AR technologythat facilitates a comfortable, natural-feeling, rich presentation ofvirtual image elements amongst other virtual or real-world imageryelements.

Systems and methods disclosed herein address various challenges relatedto AR and VR technology.

Polarizing beam splitters may be used in display systems to directpolarized light to light modulators and then to direct this light to aviewer. There is a continuing demand to reduce the sizes of displaysystems generally and, as a result, there is also a demand to reduce thesizes of the constituent parts of the display systems, includingconstituent parts utilizing polarizing beam splitters.

SUMMARY

Various implementations described herein include display systemsconfigured to provide illumination and/or image projection to the eye.Additionally or alternatively, the display systems can image the eyeand/or the environment.

In some embodiments, a head mounted display system is configured toproject light to an eye of a user to display augmented reality imagecontent in a vision field of said user. The head-mounted display systemcan include a frame that is configured to be supported on a head of theuser. The display system can also include an image projector that isconfigured to project images into the user's eye to display imagecontent in the vision field of the user. The display system can includea camera, at least one waveguide, at least one coupling optical elementthat is configured such that light is coupled into said waveguide andguided therein, and at least one out-coupling element. The at least oneout-coupling element can be configured to couple light that is guidedwithin said waveguide out of said waveguide and direct said light tosaid camera. The camera can be disposed in an optical path with respectto said at least one out-coupling optical element to receive at least aportion of the light that is coupled into said waveguide via thecoupling element and guided therein and that is coupled out from saidwaveguide by said out-coupling coupling element such that images may becaptured by said camera.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates an example of wearable display system.

FIG. 3 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes.

FIGS. 5A-5C illustrate relationships between radius of curvature andfocal radius.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked waveguide assembly in whicheach depth plane includes images formed using multiple differentcomponent colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an incoupling optical element.As discuss herein, the stack of waveguide may comprise an eyepiece.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 10 schematically illustrates a cross-sectional side view of anexample imaging system comprising an eyepiece, an image projector, alight source for illuminating the eye, and a camera for capturing animage of the eye.

FIG. 11A schematically illustrates the light source for illuminating theeye and the image projector for injecting images in the eye bothemitting light toward an incoupling optical element on a waveguide ofthe eyepiece.

FIG. 11B schematically illustrates projected light from the light sourceand from the image projector coupled into the waveguide.

FIG. 11C schematically illustrates how incoupled light may propagatethrough a waveguide by total internal reflection.

FIG. 11D schematically illustrates light from the light source and fromthe image projector coupled out of the eyepiece.

FIG. 11E schematically illustrates the waveguide and coupling opticalelement configured to propagate incoupled light at least along a fulldimension (e.g., along the x-direction) of the coupling optical element.Light entering the eye is shown from an extended source (e.g., theimaging light will capture a region of the retina).

FIG. 12A is a cross-sectional view that schematically shows lightreflected from the retina exiting the eye and incident on the eyepiece.

FIG. 12B schematically illustrates the example light coupled into thewaveguide of the eyepiece.

FIG. 12C schematically illustrates collimated incoupled light from theeye propagating through a waveguide toward an imaging device.

FIG. 12D schematically shows incoupled light from the eye propagating tothe one or more outcoupling optical elements.

FIG. 12E schematically illustrates light from the eye coupled out of thewaveguide by the outcoupling optical element and directed to the cameraso that an image of the eye (e.g., the retina) can be captured by thecamera.

FIG. 13A schematically illustrates how the imaging system can imagevarious portions of the eye, for example, of the retina, which canenable the orientation of the eye to be determined and the eye positiontracked.

FIG. 13B illustrates a pattern of sequentially displayed fixationtargets used to cause the eye to be directed in a variety of differentdirections during which the retina is imaged. The resultant imagescorrespond to non-identical portions of the retina. For example, whenthe eye is directed in various directions to view differently locatedfixation targets on the display, images captured by the camera includedifferent portions of the retina. These images can be assembled to forma larger map or composite image of the retina.

FIG. 14A schematically illustrates a cross-sectional view of an imagingsystem comprising an eyepiece and a camera for collecting light from theenvironment forward the eyepiece. Light from the environment is shownreflected off or emitted from one or more physical objects in theenvironment. Collection of light from objects in the environment infront of the eyepiece can enable images of the environment to becaptured.

FIG. 14B schematically illustrates light from the environment beingcoupled by the coupling optical element into a waveguide of theeyepiece.

FIG. 14C schematically illustrates an imaging system for collectinglight from the environment using a powered optical element, such as arefractive optical element (e.g., lens such as a wide field of viewlens), forward the eyepiece.

FIG. 15A schematically illustrates an example imaging system comprisinga polarization selective incoupling optical element for receiving lighta illumination source and coupling the light into a waveguide in aneyepiece. The eyepiece further includes a polarization selective lightcoupling element for coupling light out of the waveguide. A polarizermay be used to polarize the light from the illumination source and ahalf wave retarder may be used to rotate the orientation of the linearlypolarized light so as to be turned into the waveguide by thepolarization selective incoupling optical element.

FIG. 15B schematically illustrates light from the eye (e.g., from theretina illuminated with infrared light from the illumination source)being coupled back into the waveguide and directed to a camera for imagecapture.

FIG. 16 schematically illustrates an imaging system configured forimaging an anterior portion (e.g., cornea) of an eye. The imaging systemcomprises an eyepiece such as described above. The imaging systemfurther includes a positive lens for collimating light collect from theanterior portion of the eye for coupling via an optical coupling elementinto a waveguide and propagation to a camera for image capture. Thesystem further comprises a negative lens to offset the positive powerintroduced by the positive lens and to prevent inversion of images ofthe environment in front of the eyepiece that would otherwise be causedby the positive lens.

FIG. 17 schematically illustrates another example imaging systemconfigured for imaging an anterior portion (e.g., cornea) of an eye. Theimaging system comprises a curved wavelength selective reflector thatcollimates light from the anterior portion of the eye for coupling viaan optical coupling element into a waveguide and propagation to a camerafor image capture. The wavelength selective reflector may operate inreflection for infrared light reflected from the eye and in transmissionfor visible light from the environment in front of the user.

FIG. 18 schematically illustrates an example imaging system that alsoincludes a curved wavelength selective reflector that collimates lightfrom the anterior portion of the eye for coupling via an opticalcoupling element into a waveguide and propagation to a camera for imagecapture. Polarization selectivity may be employed to assist incontrolling the path of the light reflected from the eye. Illuminationof the eye is provided via the waveguide instead of a plurality of lightsource between the waveguide and the eye as shown in FIG. 18 .

FIG. 19 schematically illustrates an imaging system that includes ashutter to assist in a procedure for subtracting out noise.

FIGS. 20A-20E schematically illustrate an alternative procedure forsubtracting out noise using wavelength modulation in conjunction with acurved wavelength selective reflector.

FIG. 21 shows an example eyepiece that can be used to simultaneouslyproject light into a user's eye to provide image content thereto whilereceiving image data of the user's eye or of the environment in front ofthe user.

FIG. 22 illustrates a cross-sectional side view of an example of acholesteric liquid crystal diffraction grating (CLCG) having a pluralityof uniform chiral structures.

FIG. 23 illustrates an example of an imaging system comprising aforward-facing camera configured to images a wearer's eye using acholesteric liquid crystal (CLC) off-axis mirror.

FIG. 24 shows another example eyepiece that can be used tosimultaneously project light into a user's eye to provide image contentthereto while receiving image data of the user's eye or of theenvironment in front of the user. In this example, the coupling opticalelement configured to receive light in from the user's or from theenvironment in front of the user is displaced laterally from the imagecontent out-coupling optical element (e.g., exit pupil expander).

FIG. 25 shows another example eyepiece similar to that shown in FIG. 24, however, the coupling optical element configured to receive light infrom the user's or from the environment in front of the user is notlaterally spaced apart from the image content out-coupling opticalelement (e.g., exit pupil expander).

FIG. 26 shows an example eyepiece including first and second couplingoptical elements configured to couple light received from the user's orfrom the environment into a waveguide to be guided therein as well asfirst and second out-coupling optical elements configured to couplelight guided within the waveguide out of said waveguide to one or morecameras.

FIG. 27 is a cross-section through the waveguide, consolidating opticalelement, and out-coupling optical elements shown in FIG. 26 showing apolarizer in an optical path between one of the out-coupling opticalelements and the camera. The polarizer may be used to remove unwantedglint reflections form the cornea when obtaining images of the retina.

The drawings are provided to illustrate example embodiments and are notintended to limit the scope of the disclosure. Like reference numeralsrefer to like parts throughout.

DETAILED DESCRIPTION

Reference will now be made to the figures, in which like referencenumerals refer to like parts throughout.

FIG. 2 illustrates an example of wearable display system 60. The displaysystem 60 includes a display 70, and various mechanical and electronicmodules and systems to support the functioning of that display 70. Thedisplay 70 may be coupled to a frame 80, which is wearable by a displaysystem user or viewer 90 and which is configured to position the display70 in front of the eyes of the user 90. The display 70 may be consideredeyewear in some embodiments. In some embodiments, a speaker 100 iscoupled to the frame 80 and configured to be positioned adjacent the earcanal of the user 90 (in some embodiments, another speaker, not shown,may optionally be positioned adjacent the other ear canal of the user toprovide stereo/shapeable sound control). The display system may alsoinclude one or more microphones 110 or other devices to detect sound. Insome embodiments, the microphone is configured to allow the user toprovide inputs or commands to the system 60 (e.g., the selection ofvoice menu commands, natural language questions, etc.), and/or may allowaudio communication with other persons (e.g., with other users ofsimilar display systems. The microphone may further be configured as aperipheral sensor to collect audio data (e.g., sounds from the userand/or environment). In some embodiments, the display system may alsoinclude a peripheral sensor 120 a, which may be separate from the frame80 and attached to the body of the user 90 (e.g., on the head, torso, anextremity, etc. of the user 90). The peripheral sensor 120 a may beconfigured to acquire data characterizing a physiological state of theuser 90 in some embodiments. For example, the sensor 120 a may be anelectrode.

With continued reference to FIG. 2 , the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. The data include data a) captured from sensors (which may be,e.g., operatively coupled to the frame 80 or otherwise attached to theuser 90), such as image capture devices (such as cameras), microphones,inertial measurement units, accelerometers, compasses, GPS units, radiodevices, gyros, and/or other sensors disclosed herein; and/or b)acquired and/or processed using remote processing module 150 and/orremote data repository 160 (including data relating to virtual content),possibly for passage to the display 70 after such processing orretrieval. The local processing and data module 140 may be operativelycoupled by communication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 2 , in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information. In some embodiments,the remote data repository 160 may comprise a digital data storagefacility, which may be available through the internet or othernetworking configuration in a “cloud” resource configuration. In someembodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating augmented reality content, to the local processing and datamodule 140 and/or the remote processing module 150. In some embodiments,all data is stored and all computations are performed in the localprocessing and data module, allowing fully autonomous use from a remotemodule.

With reference now to FIG. 3 , the perception of an image as being“three-dimensional” or “3-D” may be achieved by providing slightlydifferent presentations of the image to each eye of the viewer. FIG. 3illustrates a conventional display system for simulatingthree-dimensional imagery for a user. Two distinct images 190, 200—onefor each eye 210, 220—are outputted to the user. The images 190, 200 arespaced from the eyes 210, 220 by a distance 230 along an optical orz-axis that is parallel to the line of sight of the viewer. The images190, 200 are flat and the eyes 210, 220 may focus on the images byassuming a single accommodated state. Such 3-D display systems rely onthe human visual system to combine the images 190, 200 to provide aperception of depth and/or scale for the combined image.

It will be appreciated, however, that the human visual system is morecomplicated and providing a realistic perception of depth is morechallenging. For example, many viewers of conventional “3-D” displaysystems find such systems to be uncomfortable or may not perceive asense of depth at all. Without being limited by theory, it is believedthat viewers of an object may perceive the object as being“three-dimensional” due to a combination of vergence and accommodation.Vergence movements (i.e., rotation of the eyes so that the pupils movetoward or away from each other to converge the lines of sight of theeyes to fixate upon an object) of the two eyes relative to each otherare closely associated with focusing (or “accommodation”) of the lensesand pupils of the eyes. Under normal conditions, changing the focus ofthe lenses of the eyes, or accommodating the eyes, to change focus fromone object to another object at a different distance will automaticallycause a matching change in vergence to the same distance, under arelationship known as the “accommodation-vergence reflex,” as well aspupil dilation or constriction. Likewise, a change in vergence willtrigger a matching change in accommodation of lens shape and pupil size,under normal conditions. As noted herein, many stereoscopic or “3-D”display systems display a scene using slightly different presentations(and, so, slightly different images) to each eye such that athree-dimensional perspective is perceived by the human visual system.Such systems are uncomfortable for many viewers, however, since they,among other things, simply provide different presentations of a scene,but with the eyes viewing all the image information at a singleaccommodated state, and work against the “accommodation-vergencereflex.” Display systems that provide a better match betweenaccommodation and vergence may form more realistic and comfortablesimulations of three-dimensional imagery.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes. With reference toFIG. 4 , objects at various distances from eyes 210, 220 on the z-axisare accommodated by the eyes 210, 220 so that those objects are infocus. The eyes 210, 220 assume particular accommodated states to bringinto focus objects at different distances along the z-axis.Consequently, a particular accommodated state may be said to beassociated with a particular one of depth planes 240, with has anassociated focal distance, such that objects or parts of objects in aparticular depth plane are in focus when the eye is in the accommodatedstate for that depth plane. In some embodiments, three-dimensionalimagery may be simulated by providing different presentations of animage for each of the eyes 210, 220, and also by providing differentpresentations of the image corresponding to each of the depth planes.While shown as being separate for clarity of illustration, it will beappreciated that the fields of view of the eyes 210, 220 may overlap,for example, as distance along the z-axis increases. In addition, whileshown as flat for ease of illustration, it will be appreciated that thecontours of a depth plane may be curved in physical space, such that allfeatures in a depth plane are in focus with the eye in a particularaccommodated state.

The distance between an object and the eye 210 or 220 may also changethe amount of divergence of light from that object, as viewed by thateye. FIGS. 5A-5C illustrate relationships between distance and thedivergence of light rays. The distance between the object and the eye210 is represented by, in order of decreasing distance, R1, R2, and R3.As shown in FIGS. 5A-5C, the light rays become more divergent asdistance to the object decreases. As distance increases, the light raysbecome more collimated. Stated another way, it may be said that thelight field produced by a point (the object or a part of the object) hasa spherical wavefront curvature, which is a function of how far away thepoint is from the eye of the user. The curvature increases withdecreasing distance between the object and the eye 210. Consequently, atdifferent depth planes, the degree of divergence of light rays is alsodifferent, with the degree of divergence increasing with decreasingdistance between depth planes and the viewer's eye 210. While only asingle eye 210 is illustrated for clarity of illustration in FIGS. 5A-5Cand other figures herein, it will be appreciated that the discussionsregarding eye 210 may be applied to both eyes 210 and 220 of a viewer.

Without being limited by theory, it is believed that the human eyetypically can interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited number of depthplanes. The different presentations may be separately focused by theviewer's eyes, thereby helping to provide the user with depth cues basedon the accommodation of the eye required to bring into focus differentimage features for the scene located on different depth plane and/orbased on observing different image features on different depth planesbeing out of focus.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. In some embodiments, the displaysystem 250 is the system 60 of FIG. 2 , with FIG. 6 schematicallyshowing some parts of that system 60 in greater detail. For example, thewaveguide assembly 260 may be part of the display 70 of FIG. 2 . It willbe appreciated that the display system 250 may be considered a lightfield display in some embodiments. In addition, the waveguide assembly260 may also be referred to as an eyepiece.

With continued reference to FIG. 6 , the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, the eachof the input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g. a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projector system 520, whichcomprises a light module 540, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 540 may bedirected to and modified by a light modulator 530, e.g., a spatial lightmodulator, via a beam splitter 550. The light modulator 530 may beconfigured to change the perceived intensity of the light injected intothe waveguides 270, 280, 290, 300, 310. Examples of spatial lightmodulators include liquid crystal displays (LCD) including a liquidcrystal on silicon (LCOS) displays. It will be appreciated that theimage injection devices 360, 370, 380, 390, 400 are illustratedschematically and, in some embodiments, these image injection devicesmay represent different light paths and locations in a common projectionsystem configured to output light into associated ones of the waveguides270, 280, 290, 300, 310.

In some embodiments, the display system 250 may be a scanning fiberdisplay comprising one or more scanning fibers configured to projectlight in various patterns (e.g., raster scan, spiral scan, Lissajouspatterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 andultimately to the eye 210 of the viewer. In some embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a single scanning fiber or a bundle of scanningfibers configured to inject light into one or a plurality of thewaveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 540 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, e.g., redirect light exiting the scanning fiber into the one or morewaveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 540, and the lightmodulator 530. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (e.g., instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, e.g., any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 2 ) in some embodiments.

With continued reference to FIG. 6 , the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6 , as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit can reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This canprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6 , the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame 80 (FIG. 2 ) and may be in electrical communication with theprocessing modules 140 and/or 150, which may process image informationfrom the camera assembly 630. In some embodiments, one camera assembly630 may be utilized for each eye, to separately monitor each eye.

With reference now to FIG. 7 , an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8 , in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 540 (FIG. 6 ) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6 ) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another. In some embodiments, each in-couplingoptical element may be offset such that it receives light without thatlight passing through another in-coupling optical element. For example,each in-coupling optical element 700, 710, 720 may be configured toreceive light from a different image injection device 360, 370, 380,390, and 400 as shown in FIG. 6 , and may be separated (e.g., laterallyspaced apart) from other in-coupling optical elements 700, 710, 720 suchthat it substantially does not receive light from the other ones of thein-coupling optical elements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6 ).

In some embodiments, the light rays 770, 780, 790 have differentproperties, e.g., different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the incoupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated incoupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7 ). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of incoupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6 . In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. As illustrated, the waveguides670, 680, 690, along with each waveguide's associated light distributingelement 730, 740, 750 and associated out-coupling optical element 800,810, 820, may be vertically aligned. However, as discussed herein, thein-coupling optical elements 700, 710, 720 are not vertically aligned;rather, the in-coupling optical elements are preferably non-overlapping(e.g., laterally spaced apart as seen in the top-down view). Asdiscussed further herein, this nonoverlapping spatial arrangementfacilitates the injection of light from different resources intodifferent waveguides on a one-to-one basis, thereby allowing a specificlight source to be uniquely coupled to a specific waveguide. In someembodiments, arrangements including nonoverlapping spatially-separatedin-coupling optical elements may be referred to as a shifted pupilsystem, and the in-coupling optical elements within these arrangementsmay correspond to sub pupils.

Eye Imaging and Environment Imaging

As discussed above, head mounted displays can be used to provide imagecontent to a user integrated with, in conjunction with, and/orsuperimposed over the view of the world in front of the wearer. Suchhead mounted display systems can be configured to project light into aneye of a user to form augmented reality image content as well as totransmit light from an environment in front of the user to the user. Ahead mounted display system may include one or more cameras for imagingthe environment and/or the user's eye. Outward facing cameras may beused for directly imaging the environment, for example, to determinewhere to place augmented reality image content with respect to objectsin the environment. For example, imaging the environment may provide thelocation of a table such that the head mounted display may render animage of person standing next to the table instead of on the table or inthe table. Inward-facing cameras may be used for directly imaging theeye such as for eye tracking. Disclosed herein are examples ofhead-mounted display systems and/or imaging systems that can beconfigured also to image the eye and/or the environment. In somedesigns, the systems do not require inward and/or outward facing camerasto directly image the eye and/or environment, respectively. Such systemsmay employ one or more cameras that are configured to receive light fromthe eye/environment via the eyepiece such as one or more waveguides inthe eyepiece that are in optical communication with the one or morecameras. With the light collected by the waveguide(s), the one or morecameras can generate images of the eye and/or the environment in frontof the user. Using the waveguide to collect the light for imaging theeye and/or environment may potentially reduce the form factor of thehead mounted display, making the head mounted display possibly morecompact and/or aesthetically desirable.

FIG. 10 illustrates an example imaging system 900 configured to imagethe eye that is integrated with an eyepiece 950 that can be used on inhead mounted display. The eyepiece 950, which can be disposed in frontof the user's eye 210 can be used to both inject image content into theeye as well as image the eye. FIG. 10 shows one eyepiece 950 in front ofone eye 210. Various head mounted display systems such as shown in FIG.2 , may include a pair of eyepieces 950 and associated componentsdisposed in front of respective left and right eyes 210. A singlewaveguide 940 is shown in FIG. 10 , but the waveguide 940 may includeone, two, three, four, six, seven, eight, or more waveguides (e.g., oneor more stacks of waveguides).

The imaging system 900 can include a light source or illumination source960 illuminating the eye to facilitate image capture, the eyepiece 950comprising a waveguide 940 configured to propagate light therein, and/oran imaging device 920 such as a camera for image capture. An imageprojector 930 for producing an image that can be injected into the eyevia the eyepiece 950 is also shown. The eyepiece 950 may include one ormore waveguides 940 configured to transport light from the illuminationsource 960 and/or image projector 930 to the eye and to transport lightfrom the eye to the camera 920. The eyepiece 950 may further compriseone or more coupling optical elements 944 for coupling light out of thewaveguide 940 and to the eye for illuminating the eye and for imageinjection and/or from the eye and into the waveguide for image capture.The eyepiece 950 may additionally comprise one or more incouplingoptical elements 942 for coupling light from the illumination source 960and/or image projector 930 into the waveguides 940 as well as one ormore outcoupling optical elements 952 for coupling light from thewaveguide out to the camera 920.

The eyepiece 950 may be disposed on a frame wearable on the head. Theeyepiece 950 may be disposed in front of the eye 210. The eyepiece 950may have a medial or nasal side closer to the nose of the wearer and anopposite lateral or temporal side closer to the temples and farther fromthe nose of the wearer. In FIG. 10 , the coupling optical element 944 ismedial or nasal with respect to the incoupling 942 and outcoupling 952optical elements (which are lateral or temporal to the coupling opticalelements 944). The illumination source 960 is also more medial or nasalwith respect to the image projector 930 (or the image projector is morelateral or temporal than the illumination source.) The relativepositions can be different, however. For example, the illuminationsource 960 may be more lateral or temporal than the image projector 930in some designs.

The waveguide 940 may comprise a sheet or layer having two majorsurfaces (a forward and a rearward surface), having the largest surfaceareas, disposed opposite one another. The forward surface may be fartherfrom the user's eye 210 (closer to the environment in front of thewearer) and the rearward closer to the user's eye (and farther from theenvironment in front of the wearer) when the user wears the head mounteddisplay. The waveguide 940 may comprise a transparent material with anindex of refraction greater than 1.0 (e.g., glass, plastic) such thatlight may be guided therein by total internal reflection between themajor surfaces. Elements with the same numbers may have the samefunctionality for one or more of the embodiments described herein.

A coupling optical element 944 for coupling light to the eye 210 fromwaveguide 940 and/or from the waveguide to the eye may be disposed on orin the waveguide 940. As shown in FIG. 10 , the coupling optical element944 may be disposed in an optical path between the user's eye 210 andthe waveguide 940 such that light coupled from the waveguide 940 via thecoupling optical element 944 may be incident on the user's eye 210 (forexample to illuminate the eye and/or for image injection). The couplingoptical element 944 may comprise a plurality of turning featuresconfigured to turn light guided within the waveguide out of thewaveguide or turn light incident on the coupling optical element 944 atan angle into the waveguide to be guided therein by total internalreflection. The coupling optical element 944 and turning features may bein physical engagement with the waveguide 940. For example, the couplingoptical element 944 may comprise a holographic or diffractive opticalelement (e.g., surface relief grating) patterned (e.g., etched) in or onthe waveguide 940. The coupling optical element 944 may comprise a layerdisposed on the waveguide 940 or may be formed in the waveguide 940. Forexample, a volume holographic or other diffractive optical element maybe formed by changing the index of refraction of material comprising thewaveguide or a layer disposed thereon. Accordingly, the coupling opticalelement 944 may be disposed in the volume of the waveguide 940 or as alayer disposed thereon.

Depending on the design, the coupling optical element 944 may betransmissive or reflective and may operate in transmission orreflection. For example, the coupling optical element 944 may include atransmissive or reflective diffractive optical element (e.g., grating)or holographical optical element that operates in transmission orreflection respectively, e.g., turning light via that is transmittedtherethrough or that is reflected therefrom. The coupling opticalelement 944 can include a polarization optical element, such as apolarization selective turning element (e.g., polarizer). Thepolarization selective turning element may include one or morepolarization gratings, diffractive optical elements, and/or holographicoptical elements and may comprise liquid crystal structures such asliquid crystal polarization gratings. The coupling optical element 944may be configured to direct light from the image projector 930 and/orlight source 960 guided within the waveguide 940 by total internalreflection (TIR) to the user's eye 210 at an angle less than (e.g., morenormal) than the critical angle so as to be ejected out of the waveguideto the eye. Additionally or in the alternative, the coupling opticalelement 944 may be configured to couple light from the eye 210 into thewaveguide 940 at an angle greater (e.g., less normal) than the criticalangle so as to be guided therein by total internal reflection to thecamera 920.

As shown in FIG. 10 , an incoupling optical element 942 for couplinglight from the illumination source 960 and/or the image projector 930into the waveguide 940 may be disposed on or in the waveguide 940. Theincoupling optical element 942 may be disposed in an optical pathbetween the light source 960 and the waveguide 940 such that lightcoupled from the light source 960 via the incoupling optical element 942is guided within the waveguide 940. The incoupling optical element 942may comprise, for example, a plurality of turning features configured toturn light incident thereon at an angle into the waveguide to be guidedtherein by total internal reflection. The incoupling optical element 942may comprise liquid crystal structures such as liquid crystalpolarization gratings. Additionally or alternatively, the incouplingoptical element 942 may include a blazed grating. The incoupling opticalelement 942 may comprise a layer disposed on the waveguide 940 or may beformed on or in the waveguide 940 (e.g., patterned) or may be otherwisemanufactured therein. For example, a surface holographic or diffractiveoptical element (e.g., surface relief grating) may be fabricated bypatterning (e.g., etching) a surface of the waveguide or a layerthereon. A volume holographic or diffractive optical element may also beformed by changing the index of refraction of material comprising thewaveguide or a layer disposed thereon. Accordingly, the incouplingoptical element 942 may be disposed in the volume of the waveguide 940or a layer disposed thereon. Depending on the design, the incouplingoptical element 942 may be transmissive or reflective and may operate intransmission or reflection. For example, the incoupling optical element942 may include a transmissive or reflective diffractive optical element(e.g., grating) or holographical optical element that operates intransmission or reflection, respectively, e.g., turning light that istransmitted therethrough or that is reflected therefrom.

The incoupling optical element 942 may comprise a reflective opticalelement (e.g., mirror). For example, the incoupling optical element 942may comprise an off-axis reflector. Additionally or alternatively, theincoupling optical element 942 and/or coupling optical element 944 caninclude a polarization optical element, such as a polarization selectiveturning element (e.g., polarizer). The polarization selective turningelement may include one or more polarization gratings, diffractiveoptical elements, and/or holographic optical elements and may compriseliquid crystal structures such as liquid crystal polarization gratings.For example, one or both of the incoupling optical element 942 and/orthe coupling optical element 944 can include liquid crystal polarizationgratings (LCPGs). LCPGs can provide high efficiency diffractionpotentially at broad wavelengths. Accordingly, LCPGs may be useful forincoupling optical elements 942 and/or the coupling optical element 944.The LCPG may be polarization dependent. The LCPG or other type of liquidcrystal grating, diffractive optical element, or optical element mayinclude a pattern or arrangement of molecules of liquid crystalconfigured to provide one or more functions such as turn light into awaveguide or out of a waveguide. Accordingly, incoupling optical element942 and/or the coupling optical element 944 may comprise polarizationgratings. Additionally or alternatively, incoupling optical element 942and/or the coupling optical element 944 can comprises liquid crystal andthus in some implementations one or both may be liquid crystal gratingsor liquid crystal diffractive optical elements. Additionally oralternatively, one or both of the incoupling optical element 942 and/orthe coupling optical element 944 can include a blazed grating. In somedesigns, the incoupling optical element 942 comprises a liquid crystalreflector, such as a cholesteric liquid crystal reflective lens (e.g.,reflective liquid crystal diffraction lens, Bragg-reflective structure,reflective liquid crystal diffraction grating, etc.). Some nonlimitingexamples of liquid crystal gratings, liquid crystal polarizationgratings and other liquid crystal optical elements are discussed in thefollowing published applications, each of which is hereby incorporatedby reference herein in its entirety and for all purposes: U.S.Publication No. 2018/0143438, titled “MULTILAYER LIQUID CRYSTALDIFFRACTIVE GRATINGS FOR REDIRECTING LIGHT OF WIDE INCIDENT ANGLERANGES,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0143485,titled “SPATIALLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS,” filedon Nov. 16, 2017; U.S. Publication No. 2018/0143509, titled “WAVEGUIDELIGHT MULTIPLEXER USING CROSSED GRATINGS,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWERREFLECTOR,” filed on Feb. 22, 2018; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017. The designs of the incoupling opticalelement 942 and/or the coupling optical element 944, however, are notlimited to these and may include other types of optical elements,diffractive optical element, liquid crystal optical element, liquidcrystal gratings and liquid crystal polarization gratings. Furtherinformation on examples of cholesteric liquid crystal structures such asreflectors may also be found below in in the section titled “CholestericLiquid Crystal Mirror.” As discussed above, other liquid crystal opticalelements as well as other non-liquid crystal optical elements may beused. Accordingly, many types of coupling optical elements (e.g.incoupling optical element 942 and/or the coupling optical element 944),diffractive optical element, gratings, polarization gratings, etc., maybe used, both those described herein as well as other types of gratings,diffractive optical elements, liquid crystal elements, and opticalelements generally. In various implementations, the incoupling opticalelement 942 may be configured to couple light from the image projector930 and/or the light source 960 into the waveguide at an angle greaterthan the critical angle so as to be guided within the waveguide 940 bytotal internal reflection to the eye to the user's eye 210.

The waveguide 940 may comprise one or more waveguides. In someimplementations, the one or more waveguides 940 comprises a stack ofwaveguides. In some designs, for example, different waveguides of thestack of waveguides are configured to output light with differentwavefront divergence as if projected from different distances from theuser's eye. For example, a first waveguide or group of waveguides may beconfigured to output light that is collimated or has a first divergenceas if projected from a first depth, and a second waveguide or group ofwaveguides may be configured to output light that is diverging (notcollimated) or is at a second divergence (greater than the firstdivergence) as if projected from a second depth closer than the firstdepth. In some designs, the different waveguides may be configured tooutput light having different associated colors. For example, a firstwaveguide may be configured to output red light, a second waveguide maybe configured to output green light, and a third waveguide may beconfigured to output blue light. A fourth waveguide may be configured tooutput and/or input infrared light.

The outcoupling optical element 952 for coupling light from thewaveguide 940 to the camera 920 such as shown in FIG. 10 may comprise,for example, a plurality of turning features configured to turn lightincident thereon at an angle such that light is not guided within thewaveguide and is turned out of the waveguide to the camera. Theoutcoupling optical element 952 may be disposed within an interior ofthe waveguide 940 or may be patterned (e.g., etched) in or on a surface(e.g., major surface) of the waveguide 940. For example, a surfaceholographic or diffractive optical element (e.g., surface reliefgrating) may be fabricated by patterning (e.g., etching) a surface ofthe waveguide or a layer thereon. A volume holographic or diffractiveoptical element may also be formed by changing the index of refractionof material comprising the waveguide or a layer disposed thereon.Depending on the design, the outcoupling optical element 952 may betransmissive or reflective and may operate in transmission orreflection. For example, the outcoupling optical element 952 may includea transmissive or reflective diffractive optical element (e.g., grating)or holographical optical element that operates in transmission orreflection, respectively, e.g., turning light that is transmittedtherethrough or that is reflected therefrom.

The outcoupling optical element 942 may comprise a reflective opticalelement (e.g., mirror). For example, the outcoupling optical element 952may comprise an off-axis reflector. In some designs, the outcouplingoptical element 952 can include a polarization optical element, such asa polarization selective turning element (e.g., polarizer). Accordingly,the polarization selective turning element may include one or morepolarization gratings, diffractive optical elements, and/or holographicoptical elements and may comprise liquid crystal structures such asliquid crystal polarization gratings. In some implementations, forexample, the outcoupling optical element 952 can include liquid crystalpolarization gratings (LCPGs). LCPGs can provide high efficiencydiffraction potentially at broad wavelengths. Likewise, LCPGs may beuseful for outcoupling optical element 952. The LCPG may be polarizationdependent. The LCPG or other types of liquid crystal gratings mayinclude a pattern or arrangement of molecules of liquid crystalconfigured to provide one or more functions such as turn light into awaveguide or out of a waveguide. Accordingly, outcoupling opticalelement 952 may comprise polarization gratings. Additionally oralternatively, outcoupling optical element 952 can comprises liquidcrystal and thus in some implementations may be liquid crystal gratingsor other liquid crystal optical element such as liquid crystaldiffractive optical elements. Additionally or alternatively, theoutcoupling optical element 952 can include a blazed grating. In somedesigns, the outcoupling optical element 952 comprises a liquid crystalreflector, such as a cholesteric liquid crystal reflective lens (e.g.,reflective liquid crystal diffraction lens, Bragg-reflective structure,reflective liquid crystal diffraction grating, etc.). Some nonlimitingexamples of liquid crystal gratings, liquid crystal polarizationgratings and other liquid crystal optical elements are discussed in thefollowing published applications, each of which is hereby incorporatedby reference herein in its entirety and for all purposes: U.S.Publication No. 2018/0143438, titled “MULTILAYER LIQUID CRYSTALDIFFRACTIVE GRATINGS FOR REDIRECTING LIGHT OF WIDE INCIDENT ANGLERANGES,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0143485,titled “SPATIALLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS,” filedon Nov. 16, 2017; U.S. Publication No. 2018/0143509, titled “WAVEGUIDELIGHT MULTIPLEXER USING CROSSED GRATINGS,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWERREFLECTOR,” filed on Feb. 22, 2018; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017. The designs of the outcoupling opticalelement 952, however, are not limited to these and may include othertypes of optical elements, diffractive optical element, liquid crystaloptical element, liquid crystal gratings and liquid crystal polarizationgratings. Further information on examples of cholesteric liquid crystalstructures such as reflectors may also be found below in the sectiontitled “Cholesteric Liquid Crystal Mirror.” As discussed above, otherliquid crystal optical elements as well as other non-liquid crystaloptical elements may be used. Accordingly, many types of couplingoptical elements (e.g. outcoupling optical element 952), diffractiveoptical element, gratings, polarization gratings, etc., may be used,both those described herein as well as other types of gratings,diffractive optical elements, liquid crystal elements, or opticalelements generally. As referred to above, the outcoupling opticalelement 952 may be configured to redirected light guided within thewaveguide 940 at an angle less than the critical angle so as not to beguided within the waveguide by total internal reflection but to beejected out to the camera 920.

In various designs, the coupling optical element 944 may be transparentin the visible spectrum such that the user can see through the couplingoptical element 944 and the eyepiece 950 to the environment in front ofthe user. The incoupling optical element 942 may also turn light in thevisible spectrum, for example, if the incoupling optical element is usedto receive light from the image projector 930 and/or if the illuminationsource 960 is configured to output visible light to illuminate the eye210 with visible light. In some embodiments, the incoupling opticalelement 942 is configured to turn infrared light, for example, if theillumination source 960 is configured to output infrared light toilluminate the eye 210 with infrared light. In some designs such asshown in FIG. 10 , the incoupling optical element 942 may be more medialor nasal than the outcoupling optical element 952. However, in otherdesigns the incoupling optical element 942 may be more lateral ortemporal than the outcoupling optical element 952. In certainimplementations such as shown in FIG. 10 , the outcoupling opticalelement 952 may be adjacent the incoupling optical element 942 althoughnon-adjacent positioning is possible.

The illumination source 960 may be disposed on the same side of theeyepiece 950 as the eye 210 (e.g., rearward or proximal side), as shownin FIG. 10 . (Proximal may refer to the side closest to the eye 210.)Alternatively, the illumination source 960 may be disposed on the sideopposite the eye 210 (e.g., forward or distal side). The illuminationsource 960 may be configured to direct light into at least one of themajor surfaces of the waveguide 940 via the incoupling optical element942. The light source 960 may be configured to emit invisible light(e.g., infrared). The light source 960 may include one or more LEDs. TheLEDs may comprise infrared LEDs. The light source 960 may be configuredto emit coherent light. In some designs, the light source 960 comprisesa laser (e.g., infrared laser). In some designs, the light source 960emits pulsed light. For example, the camera 920 can be configured tocapture an image periodically. Accordingly, the illumination source 960can be pulsed to coincide with the period during which the cameraobtains images. The intensity output from the illumination source 960can be reduced when the camera is not obtaining an image. Byconcentrating the total energy of the illumination on a short timeincreased signal to noise can be obtained while not exposing the eye 210to unsafe intensity levels. In some cases, for example, the camera 920captures one image every 30 milliseconds and the exposure time of thecamera is few milliseconds. The illumination source 960 can beconfigured to output pulses having similar period and duration to matchthat of the camera 920.

In some implementations, different light sources having differentwavelengths are alternately pulsed to provide different wavelengthillumination at different times as discussed below.

The incoupling optical element 942 may be in direct opticalcommunication with the illumination source 960 and/or image projector930, for example, so as to guide light from said image projector 930and/or light source 960 therein. For example, light emitted by the lightsource 960 may be incident on the incoupling optical element 942 beforeoptically interacting with either the coupling optical element 944and/or outcoupling optical element 952.

As shown in FIGS. 11A-11E, light 902 projected from the image projector930 may form an image on the retina. The image projector 930 may includea light source, a modulator, and/or projection optics. The light sourcefor the image projector 930 may comprise one or more LEDs, lasers orother light sources and may comprises one or more visible light sources.The modulator may comprise a spatial light modulator such as a liquidcrystal spatial light modulator. Such a spatial light modulator may beconfigured, for example, to modulate the intensity of light at differentspatial locations. The projection optics may comprise one or morelenses. Other types of image projectors 930 capable of projecting and/orforming images may be employed. For example, the image projector 930 maycomprise a scanning optical fiber.

The image projector 930 and the incoupling optical element 942 may be indirect optical communication with each other. The image projector 930may, for example, be aligned with the incoupling optical element 942into which light from the image projector 930 is directed. In somecases, image projector 930 is disposed adjacent the correspondingincoupling optical element 942 and/or the waveguide 940. The imageprojector 930 may also be disposed in an optical path that includes theincoupling optical element 942, the coupling optical element 944, andthe eye 210.

The image projector 930 may be a separate element than the illuminationsource 960, as shown in FIG. 10 as well as in FIGS. 11A-11E. However, insome cases the image projector 930 may be used as the illuminationsource. For example, in addition to injecting images into the eye 210,the image projector 930 may be used to direct visible and/or infraredlight into the eye to illuminate the eye for image capture.Alternatively, however, one or more separate light sources 960 may beused to illuminate the eye 210 for image capture.

The light emitted by the illumination source 960 may comprise aparticular wavelength range of light such as, for example, invisiblelight. The illumination source 960 may be configured to projectinvisible (e.g., infrared) light onto/into the eye 210 for imaging oneor more parts (e.g., cornea, retina) of the eye 210. In certain exampleimplementations, the light source 960 may be configured to emit light inthe range of between about 850 nm and 940 nm. The light source 960 maybe configured to emit light extending over a wavelength range of atleast about 20 nm. Other ranges are also possible. The wavelength rangeemitted may be 5 nm, 10 nm, 15 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm,or any range between any of these values. The light source 960 may beconfigured to emit light across a broad band of wavelengths, such as anyrange within the infrared spectrum.

The imaging device 920, which may comprise a camera, may comprise adetector array and possibly imaging optics. The detector array maycomprise, for example, a CCD or CMOS detector array and the imagingoptics may comprise one or more lenses. The one or more lenses may havepositive optical power and an associated focal length. In certaindesigns, the camera 920 is focused at infinity. For example, the opticsmay have a focal length, f, and detector array may be disposed adistance away from the optics corresponding to the focal length suchthat objects at a large distance are imaged onto the detector array.Similarly, light from the eye or objects in the environment that iscollimated will be focus on the detector array to form an image of theeye or object thereon.

The imaging device 920 may be disposed on the opposite side of thewaveguide 940 as the illumination source 960 and/or the eye 210. In somedesigns, the imaging device 920 may be disposed on the same side of thewaveguide 940 as the light source 960 and/or eye 210. As shown in FIG.10 , the imaging device 920 may be disposed near a lateral or temporaledge of the eyepiece 950 although other locations are possible.

FIGS. 11A-11E illustrate the operation of the example imaging system 900of FIG. 10 . FIG. 11A shows the illumination source 960 emitting light902 toward the incoupling optical element 942 on the waveguide 940. Asshown, the light 902 can be directed generally at normal incidence tothe eyepiece 950 although other angles are possible. In some designs,the light source 960 is configured to emit collimated light into theeyepiece 950. As shown in FIG. 11B, the illumination light 902 can becoupled into the waveguide 940 via the incoupling optical element 942.In some designs where the incoupling optical element 942 comprises adiffractive optical element (e.g., grating, holographic element) thelight incident thereon is diffracted at an angle greater than thecritical angle of the waveguide to cause the incoupled light 904 to beguided within the eyepiece 950 by total internal reflection (TIR). Insome designs, the incoupling optical element 942 may be configured todirect light toward the coupling optical element 944. The incouplingoptical element 942 may be polarization selective. For example, theincoupling optical element 942 can include a polarization selectiveturning element such a polarization grating like a liquid crystalpolarization grating. FIG. 11C shows how the incoupled light 904propagating through the waveguide 940 by TIR.

FIG. 11D illustrates an example imaging system 900 coupling light out ofthe eyepiece 950. As the incoupled light 904 propagates through thewaveguide 940, some of the light may be incident on the coupling opticalelement 944. The coupling optical element 944 can be configured tocouple the incoupled light 904 out of the eyepiece 950 and toward theuser's eye 210. The coupling optical element 944 may be configured tocouple the light as collimated light toward the eye 210. The couplingoptical element 944 may be tuned to light of a particular wavelengthrange. For example, the coupling optical element 944 may be configuredto couple infrared light (e.g., between about 700 nm and 15000 nm) outof the waveguide 940. In some designs, the coupling optical element 944can be configured to couple multiple wavelengths of light out of theeyepiece 950. For example, the coupling optical element 944 may be tunedfor both infrared and visible light. The coupling optical element 944can also be configured to couple light into the waveguide 940, asdescribed more fully below.

The coupling optical element 944 can be configured to increase one ormore dimensions of an eyebox for a user. For example, the one or moredimensions may be measured along a first axis (e.g., x axis). Theeyepiece 950 may further include an orthogonal pupil expander (OPE). TheOPE may have at least one light redirecting element disposed on or inthe waveguide (e.g., on one of the major surfaces) or the OPE may bedisposed within the waveguide 940. The OPE may include features similaror identical to those described above for light distributing elements730, 740, 750 above. In some implementations, the light redirectingelement may comprise a diffractive optical element. The OPE may beconfigured to increase a dimension of the eyebox along a second axis(e.g., y axis) orthogonal to the first axis.

FIG. 11D shows some of the light exiting the eyepiece 950 toward theuser's eye 210. In some designs, the coupling optical element 944 isconfigured such that incoupled light 904 that is incident on thecoupling optical element 944 at various portions of the coupling opticalelement 944 along the first axis (e.g., parallel to the x-axis) exitsthe eyepiece 950 at each portion of the coupling optical element 944along the first axis. This may provide a user with a light forprojecting images or illuminating the eye for different eye positions orlocations.

As shown in FIGS. 11D-11E, the coupling optical element 944 may beconfigured to couple the incoupled light 904 out of the eyepiece 950 ascollimated light. This light may also be directed in general near normalrelative to a major surface of the eyepiece 950 and/or waveguide 940.The collimated light may be directed into the eye and focus by the eye(e.g., the cornea and natural lens of the eye) onto the retina. Thislight 908 incident on the retina may be provide illumination for imagingthe retina and/or providing image content to the eye. Some of this light908, for example, may be reflected or scatter off the retina, exitingthe eye and providing for images of the retina to be captured. The lightsource 960 may be an extended light source such that the light willilluminate a region of the retina.

FIGS. 12A-12E illustrate how the imaging system 900 of FIGS. 11A-11E mayadditionally or alternatively be used for image collection of the eye210. FIG. 12A shows light 910 reflected from the retina exiting the eye210. As shown, the light 910 scattered or reflected from the retina thatpasses through the natural lens of the eye, the pupil in the eye and thecornea from may be collimated. This light may also be incident on theeyepiece 950 at normal incidence (e.g., at a right angle to a majorsurface of the waveguide 940 and/or coupling optical element 944). Thecoupling optical element 944 may be configured to couple the light 910reflected from the retina into the waveguide 940.

FIG. 12B illustrates an example imaging system 900 as it couples lightinto the eyepiece 950. The coupling optical element 944 may include aturning feature such as a diffractive optical element, or otherstructures that redirect the light at an angle greater than the criticalangle so as to be guided within the waveguide 940. The coupling opticalelement 944 may be configured to direct the incoupled light 914generally toward the light source 960 and/or the imaging device 920. Thecoupling optical element 944 can be configured to couple less than afraction of this light propagating toward the camera 920 back out of thewaveguide 940. For example, a partially reflective element (e.g.,semi-transparent mirror) may be disposed on or in the waveguide 940 suchthat a portion of the incoupled light 914 continues to propagate withinthe waveguide 940 by total internal reflection while reducing leakage ofthe incoupled light 914 out of the waveguide 940 along portions of thewaveguide 940 where the coupling optical element 944 is disposed. Theportion of light that does not leak out may be any fraction between 0and 1. For example, the portion may be 0.90, where 90% of the light rayspropagating through the waveguide 940 along the coupling optical element944 are maintained within the waveguide 940 at each reflection of thelight rays. Other portions are possible (e.g., 0.10, 0.20, 0.30, 0.40,0.50, 0.60, 0.70, 0.80, or any range between any of these values). Suchpartially reflective element(s) can similarly be used in implementationsdescribed below.

As shown in FIG. 12C, collimated incoupled light 914 may continue topropagate through the waveguide 940 toward the imaging device 920. FIG.12D shows how some of the incoupled light 914 can continue to propagateuntil it is incident on one or more outcoupling optical elements 952. Inorder to reduce the amount of leakage of incoupled light 914 out of theincoupling optical element 942, the incoupling optical element 942 canbe configured to couple little of this light propagating toward thecamera 920 back out of the waveguide. For example, a partiallyreflective element (e.g., semi-transparent mirror) may be disposed on orin the waveguide 940 such that the a portion of the incoupled light 914continues to propagate within the waveguide 940 by total internalreflection while reducing leakage of the incoupled light 914 out of thewaveguide 940 along portions of the waveguide 940 where the incouplingoptical element 942 is disposed. The portion of light that does not leakout may be any fraction between 0 and 1. For example, the portion may be0.90, where 90% of the light rays propagating through the waveguide 940along the coupling optical element 944 are maintained within thewaveguide 940 at each reflection of the light rays. Other portion may bepossible (e.g., 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or anyrange between any of these values). Such partially reflective element(s)can similarly be used in implementations described below.

As shown in FIG. 12E, the outcoupling optical element 952 can beconfigured to couple light guided within the waveguide 940 out of thewaveguide 940 and to the imaging device 920. As a result, lightpropagating in the waveguide 940 that is incident on the outcouplingelement 952 may be redirected so as to be ejected out of the waveguide940, for example, out of a major surface of the waveguide 940 (e.g., theforward or rearward side of the waveguide 940) and directed on theimaging device 920. The outcoupling optical element 952 may beconfigured to direct the light 926 to exit the waveguide 940perpendicular (e.g., normal) to the major surface of waveguide 940. Insome designs, the outcoupling optical element 952 is configured todirect collimated light 924 onto the imaging device 920 at normalincidence to a light sensitive portion of the imaging device 920. Asdiscussed above, the camera 920 may be infinity focused, for example,the imaging optics may be configured to focus collimated light onto thedetector array.

Accordingly, the waveguide 940 may be configured to guide light coupledfrom the user's eye 210 into the waveguide 940 to be received by theimaging device 920 (e.g., camera) so as to capture an image of at leasta portion of the eye 210 of the user. The same waveguide 940 may beconfigured to guide light coupled from the image projector 930 such thatlight from the image projector 930 can be directed to the user's eye 210such that the image from the image projector 930 is in the vision fieldof the user. In some implementations, the same waveguide is configuredto guide light coupled from the illumination source 960 such that lightfrom the illumination source can be directed to the user's eye 210 toilluminate the eye such that an image of the eye can be captured by thecamera 920.

In some implementations, the same coupling optical element 944 can beconfigured to (i) couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920 and (ii) couplelight from the image projector 930 out from the waveguide 940 to theuser's eye 210 to project image content into the user's vision field. Insome implementations, the same coupling optical element 944 can beconfigured to couple light from the illumination source 960 out of thewaveguide to the user's eye 210 such that light from the illuminationsource can illuminate the eye.

In other designs, different waveguides can be used and/or differentcoupling optical elements 944 can be used. In some designs for example,a first waveguide 940 may be configured to guide light coupled from theuser's eye 210 to be received by the camera 920 so as to capture animage of at least a portion of the eye 210 of the user and a secondwaveguide may be configured to guide light coupled from the imageprojector 930 such that light from the image projector 930 can bedirected to the user's eye 210. The first and second waveguides may bestacked on top of one another. Another waveguide may in addition or inthe alternative be configured to guide light coupled from theillumination source 960 such that light from the illumination source canbe directed to the user's eye 210 to illuminate the eye.

Also, in some implementations, a first coupling optical element 944 canbe configured to (i) couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920 and (ii) couplelight from the image projector 930 out from the waveguide 940 to theuser's eye 210 to project image content into the user's vision field.Another coupling optical element may in addition or in the alternativebe configured to coupled light from the illumination source 960 out ofthe waveguide to the user's eye 210 such that light from theillumination source can illuminate the eye.

In some designs, the coupling optical element 944 can include aplurality of diffractive optical elements (DOEs). For example, a firstDOE can be configured to couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920. A second DOE canbe configured to couple light from the image projector 930 out of thewaveguide 940 to the user's eye 210 to project image content into theuser's vision field. Optionally, a third DOE can be configured to couplelight from the light source 960 out of the waveguide 940 to the user'seye 210 to illuminate the eye. The first and second (and possibly third)DOEs can be stacked, e.g., in some implementations such that light fromthe environment in front of the user passes through the first DOE and isthen incident on the second DOE and then incident on the third DOE andincident on the user's eye. The order, however, may be different.

In some designs, the first and second DOEs are integrated in a singleelement or volume of the waveguide 940. In some implementations, forexample, both the first and second DOEs are superimposed on each other(e.g., occupy the same or approximately the same volume) within thewaveguide 2102. For example, the first and second DOE may be recorded inthe same medium.

As described above, image capture of the eye, e.g., of the retina, canfacilitate eye tracking. FIG. 13A, for example, illustrates the imagingsystem 900 configured to image various portions of the eye 210 (e.g.,retina), for example, at different times when the eye is in differentpositions. Stages A and B may refer to images of the eye 210 duringdifferent orientations of the eye. FIG. 13A shows imaging of the eye 210and the results thereof during both stage A and stage B imaging.

In some implementations, the light emission 928 (e.g., from anillumination source 960 such as described above or from one or moreilluminations sources configured and/or located differently) can be usedto obtain one or more images of the retina 962, as shown by FIG. 13A.The image of the retina 962 may comprise one or more regions 964, 966that are imaged during different orientations of the eye 210. FIG. 13Ashows two regions 964, 966 of the image of the retina 962. For example,the region 964 of retina imaged in stage A may be imaged while the eye210 is directed at an angle normal to the waveguide 940. The image datafor the region 966 of retina imaged in stage B may be obtained while theeye 210 is oriented at an acute angle with the waveguide 940. Using oneor more orientations of the eye 210 during one or more stages ofimaging, a composite image or map of the retina 962 may be obtained.Processing electronics or a processor, such as data module 140 (see FIG.2 ), may be used to find overlapping image data between two neighboringregions. Using the overlapping regional image data, a composite image orof the retina 962 can be determined. A larger size (e.g., full-size)composite image or map of the user's retina can be stored.

As described herein, the head mounted display can be used to map auser's eye retina based on the direction that user's eye is directed. Toprovide a realistic and intuitive interaction with objects in the user'senvironment using eye gaze and/or to identify a wearer of the headmounted display device, the head mounted display system can use retinalmapping to incorporate a uniqueness of a user's eye features and otherconditions that may have some effect on eye measurements. For example,the images may be identified based on positions of blood vessels in thecorresponding retinal image.

Retinal mapping can involve a process for enabling a computing device tolearn how to associate a user's eye gaze (e.g., as identified in retinalimages) with gaze points in a 2D or 3D space. An eye gaze may beassociated with a single point in the 2D or 3D space. An eye gaze canalso be associated with multiple points in the space, which can describea movement of a virtual object (e.g., a series of points, a location ofa moving image).

The head mounted display system can determine a user's eye gaze based onretinal images. The head mounted display system can obtain retinalimages using sensors (e.g., eye cameras such as the imaging device 920).The head mounted display system can image one or both eyes of the userwhile the user changes his or her eye gazes (such as, e.g., when theuser is looking around to follow a moving or shifting calibration targetor fixation target). To map a user's retina, the head mounted displaysystem can present a virtual target, e.g., a fixation target, for theuser to look at. The virtual target may be associated with one or moreknown points of gaze in the 2D or 3D space. While the user is looking atthe target, the head mounted display system can acquire retinal image(s)and associate the image(s) with gaze point(s). The head mounted displaysystem can calculate and/or generate a mapping matrix based on theassociations of respective retinal images and points of gaze associatedwith the target.

The retinal mapping result can reflect uniqueness in each person's eyes.For example, the head mounted display system can generate a mappingmatrix customized to one or both eyes of a specific individual. Forexample, the users may have different amounts of eye movements or eyegazes in response to a specific target. Additionally or alternatively,the user may have a different position, size, shape, and/or orientationof blood vessels in the retina. As a result, by generating a calibrationresult specific to an individual user, the head mounted display systemmay allow more accurate user interactions with eye gazes and/or mayallow for identification a particular user.

Accordingly, when a user puts on the head mounted display device, thesystem can detect whether the user is a previous user or a new user. Aconfusion matrix can be calculated where a score for a particular eyegaze image stored in the system memory is compared to a correspondingimage of the current user. The confusion matrix can include a comparisonscore for a plurality of eye gazes and associated retinal images. Basedon the comparison scores, the system may be able to make a determinationwith regard to an identity of the user (e.g., whether the user is thesame as the individual for which the stored retinal images or compositemap are associated) and/or a confidence level for the determination. Theconfidence level may, for example, include an identity coefficient.Stored images, for example, a composite image or map, may be comparedwith later obtained images referred to as instantaneous or real-timeimages obtained for a current user. The system may provide an alert ifthe system detects that the user is a new user or may take other action.

The system may apply filtering such as digital filtering or imageprocessing to the images of the retina captured by the camera. Suchfiltering or imaging processing, may for example, enhance features thatmay be used for identification, stitching, assembling a compositeimages, eye tracking, etc. Such filtering or image processing maycomprise edge enhancement. Such a filter may comprise, for example, aFrangi filter although other types of filters may be used. Such a filteror processing (e.g., edge enhancement or a Frangi filter) can be used toenhance and/or detect images features such as vessels or tubularstructures or fibers in retinal images.

FIG. 13B illustrates a pattern of sequentially displayed fixationtargets that can be used in the retinal mapping process. These virtualtargets on which a user's eye will direct their gaze can cause the eye'sgaze to be redirected to a variety of different directions during whichthe retina can be imaged. The resultant images associated with thedifferent gaze directions correspond to non-identical portions of theretina. As discussed above, when the eye is gazing in differentdirections to view differently located fixation targets on the display,images captured by the camera include different portions of the retina.These images can be assembled to form a larger map or composite image ofthe retina.

FIG. 13B shows a virtual target at sixteen different location in auser's field of view (FOV) 1200. In various implementations, the virtualtarget would be presented at a given location at a given time. One ormore retinal images would be obtained during a time when the virtualtarget is presented at that particular location to a user. This image orthese images may be associated with that target position and/or acorresponding gaze direction. Greater or fewer target locations may beused. In the example shown in FIG. 13B, the sixteen targets locations1202 a-1202 p are shown. More or less target locations may be used. Thetarget locations may also be different. The order at which the targetsare presented at the different locations may vary. For example, thetarget may move in a raster pattern from the left to the right side ofthe field of view of the user, back to from the right to the left, andagain from the left to the right, lowering the position of the target inthe field of view with each lateral pass across the field of view.However, other patterns and approaches are possible. Likewise, thetarget can be rendered identically or differently at the differentlocations. For example, the target rendered may be different sizes,shapes, colors, etc. The targets can be rendered sequentially to a userduring the eye tracking calibration process. For example, as discussedabove the head mounted display system may render target in a serpentinepattern. For example, the target 1202 a may be followed by 1202 b, then1202 c, then 1202 d, then 1202 h, then 1202 g, and so forth. Otherpatterns are possible. For example, the target could be displayed inmore random or non-sequential patterns. In some embodiments, a singletarget is displayed to the user, and the target moves around the user'sfield of view (for example, passing or temporarily stopping at thepositions 1202 a-1202 p during the target's movement). The head mounteddisplay system can acquire an image of the user's retina(s) while theuser is looking at these targets. For example, the head mounted displaysystem can acquire a first image when the user is looking at the targetat the first location 1202 a while acquiring a second image when theuser is looking at the target at a second location 1202 b, and a thirdimage when the user is looking at the target at a third location 1202 c,and so forth. The wearable system can associate the first image to thefirst position 1202 a and associate the second image with the secondposition 1202 b, and the third image with the third position 1202 c, andso forth. Neighboring images may be stitched together in a database tocreate a full or partial retinal map. For example, two image can bestitched together in appropriate registration using features or portionsof the feature (e.g., blood vessels or portions thereof) that are commonto the multiple images. In various implementations, adjacent targetpositions would produce overlapping images that can be registered andstitched together. For example, target position 1202 a and targetposition 1202 b as well as target position 1202 b and target position1202 c may produce overlapping and adjacent retinal images that can bestitched with each other. Accordingly, a number of different retinalimages may be obtained with different eye gazes so as to assemble alarger image (e.g., a composite image or map) of the retina.

As discussed above, eye tracking can be performed using the compositeretinal image or map. For example, after the target is no longerdisplayed, the user may move their eye gaze about as the user looks atdifferent real objects in front of the user and head mounted display oraugmented reality (virtual) image content displayed by the head mounteddisplay. One or more retinal images may be obtained at these times. Theterm “instantaneous” or “real-time” images may be used herein todescribe these images obtained subsequent to calibration that can beused for eye tracking (or other purpose such as obtaining biometricdata). These “instantaneous” or “real-time” images likely correspond toa portion of the composite retinal image or map. The system may beconfigured to sufficiently match this “instantaneous” or “real-time”retinal image with a portion of the composite retinal image or retinalmap. Such matching may be based on features or portions of features(blood vessels or portions thereof) that are common to both the“instantaneous” or “real-time” retinal image and the portion of thecomposite retinal image or map. Based on the location the portion of thecomposite retinal image or map to which this “instantaneous” or“real-time” retinal image coincides, a gaze direction may be deduced.Different gaze directions will result in retinal images that correspondto different portions of the retinal map. Accordingly, identifying thelocation of the “instantaneous” or “real-time” retinal image on thecomposite retinal image or map will provide information as to thedirection of the user's gaze. Eye tracking, for example, tracking themovement of the eye and the change in eye gaze may be performed usingsuch or similar methods. As discussed above, edge enhancement, edgedetection, or other digital filtering and/or processing may be used toenhance and/or correlate features of different images with the compositeretinal image or retinal map.

In various implementations after completion of the initial calibrationprocess where the virtual target or fixation target is displayed (e.g.,at a plurality of locations) to assemble a composite retinal image ormap, the composite retinal image or map can still be refined. Forexample, as additional retinal images are obtained, the compositeretinal image or map can be further refined or improved using theadditional images. Accordingly as additional “instantaneous” or“real-time” retinal images are obtained, for example for the purpose ofproviding eye tracking, the composite retinal image or map can befurther refined or improved using the “instantaneous” or “real-time”. Asa user continues to look at various positions in the display (with orwithout aid of a calibration target), the retinal composite image or mapmay be further refined using additional images are acquired subsequentto the initial calibration where the virtual target or fixation targetwas displayed. The quality of the composite retinal image or map maytherefore be increased.

Additional non-limiting examples of how eye tracking may be accomplishedand/or a composite retinal image or map may be produced and retinalimages used are described in U.S. Publication No. 2017/0205875, titled“EYE IMAGE COLLECTION,” filed on Jan. 17, 2017, the disclosure of whichis hereby incorporated herein by reference in its entirety.

Accordingly, as discussed above larger portions of the retina may berecorded and mapped by obtaining retinal images and/or other images ofthe eye using imaging systems such as described herein and such imagesmay facilitate eye tracking. For example, an image of the eye 210 shownin FIG. 13A may be captured when the eye is in an arbitrary position.The processing electronics or a processor (such as the same or differentone described above as forming the composite image) may then comparecaptured images of the user's retina in real time to the storedcomposite or larger size (e.g., full-size) image of the user's retina totrack eye movement. A given image of the user's retina captured in realtime may show a specific portion of the user's retina. As describedabove, by comparing such a captured image to the stored image of theuser's mapping a larger portion of the user's retina, the system candetermine which portion of the user's retina is shown in the capturedimage, and can thereby determine the position/orientation of the eyethat would produce such an image. See for example FIG. 13A, which showstwo different images of portions of the retina that are produced whenthe eye is in two different positions and/or orientations. Accordingly,the position and/or orientation of the eye may be determined bycapturing different images of the retina and determining which portionof the retina is visible. Such determination may be performed even if acomposite image is not formed but rather multiple images of the retinafor different eye positions/orientations are recorded and stored in adatabase. When a future image of the retina is obtained, that image maybe compared to images in the database of stored images to determinewhich image in the database resembles the image of the eye recentlyobtained. Matching the recent image to one or more of the images in thedatabase having associated positions and/or orientations associated withthem can enable determination of the orientation and/or position of themore recent image. Other approaches to eye tracking may be used based onthe images captured using the designs described herein.

As described herein, the retinal images may be employed for otherpurposes as well. For example, the retinal images may be used to verifythat the user is the same user for which the composite retinal image ormap was obtained. An image of the retina that is obtained when a user iswearing the head mounted display system (e.g., during the calibrationprocess and/or during later use) may be compared with a previouslyobtained composite retinal image or map (e.g., created a prior day orwhen the head mounted display was previously booted up) that is stored.If the recently obtained retinal image does not match a portion of thecomposite retinal image or map sufficiently enough, a conclusion may bemade that the current user is different than the previous user (e.g.,for which the composite virtual image or map was created). Such methodsmay be used for security, e.g., to verify that the current user of thehead mounted display device is the owner or typical user of the device.Accordingly, biometric data obtained via retinal imaging may be used forsecurity purposes.

The retinal imaging may be used as well to collect biometric data formonitoring the user's health. Medically related data may be obtainedfrom the retinal images. Such medical data may be useful for monitoringthe health of the user.

Although various applications of eye imaging, such as eye tracking,collection of biometric data for heath monitoring and for security arediscussed herein in the context of retinal imaging, imaging other partsof the user, for example, of the user's eye may be employed for theseand other purposes.

Although the eyepiece 950 is described above as capable of beingutilized to facilitate imaging of the eye, the eyepiece can also be usedto image the world in front of the user. FIGS. 14A-14B, for example,illustrate an example imaging system 900 that can be used to image aportion of an environment in front of the user and/or objects in theportion of the environment. The imaging system 900 used may be a similarsystem as described for FIGS. 11A-11E and/or for FIGS. 12A-12E exceptthat light is collected by the eyepiece 950 from the environment forwardthe eyepiece and the user. FIG. 14A, for example, illustrates light 970from the environment that is reflected off and/or emitted by one or morephysical objects 972 in the environment forward the user and eyepiece950. As shown, the light 970 from the environment may be approximatelycollimated (e.g., at infinity), for example because the physical object972 in the environment may be located at a sufficiently large distancefrom the imaging system 900 for the light rays reaching the imagingsystem 900 to be collimated or approximately collimated. In someimplementations, the imaging system 900 may be configured to image theenvironment and/or objects in the environment without the use of anyoptical elements having optical power (e.g., lenses, mirrors) in theimaging system 900.

The imaging system 900 shown in FIGS. 14A and 14B is similar to theimaging systems described above. The imaging system includes theeyepiece 950 comprising one or more waveguides 940 including thecoupling optical element 944 configured to direct light from an imageprojector 930 (not shown) into the eye 210 to form images therein. Theone or more waveguides may include a plurality of waveguides (e.g., astack of waveguides) configured to incouple/outcouple a plurality ofcorresponding colors/wavelengths. Each waveguide in a stack ofwaveguides may be configured to direct light of a particular color(e.g., red, green, blue). For example, a distalmost waveguide (e.g.,stack of waveguides) may be configured for visible light (e.g., red,blue, green) such that the waveguide is configured to incouple andoutcouple the same wavelength(s) of visible light. Additionally oralternatively, a waveguide configured to incouple and outcoupleinvisible (e.g., infrared) light may be disposed proximal the eye 210.Such a plurality of waveguides corresponding to the waveguide 940 may beused in any other implementation described herein. The imaging system900 may also include the imaging device (e.g., camera) 920 andoutcoupling optical element 952 configured to turn light reflected fromthe eye 210 that is propagated within the waveguide 940 to the camera.In FIGS. 14A and 14B, the illumination source 960 is excluded since anillumination source may not be needed to image the environment in frontof the user. However, an illumination source (e.g., the light source 960described above) may be used in certain designs.

The eyepiece 950, waveguide 940, coupling optical element 944,outcoupling optical element 952 and camera 920 may be the same orsimilar to that describe above. For example, the coupling opticalelement 944 may be in physical engagement with the waveguide 940. Forexample, the coupling optical element 944 and/or outcoupling opticalelement 952 may be disposed in an optical path between the environmentin front of the eyepiece 950 and camera 920 such that light from theenvironment is coupled into the waveguide 940 via the coupling opticalelement 944 and coupled out of the waveguide via the outcoupling opticalelement to be incident on the camera 210 (for example to form an imageof at least a portion of the environment). The coupling optical element944 may comprise a plurality of turning features configured to turnlight guided within the waveguide out of the waveguide or turn lightincident on the coupling optical element 944 at an angle into thewaveguide to be guided therein by total internal reflection. Theoutcoupling optical element 952 may comprise a plurality of turningfeatures configured to turn light (from the environment) that is guidedwithin the waveguide at an angle such that the light is not guided inthe waveguide by total internal reflection but is direct out toward thecamera. The coupling optical element 944, outcoupling optical element952 and the turning features associated with each may be in physicalengagement with the waveguide 940. For example, the coupling opticalelement 944 and/or outcoupling optical element 952 may comprise one ormore holographic or diffractive optical elements (e.g., surface reliefgratings) patterned (e.g., etched) in or on the waveguide 940. Thecoupling optical element 944 and/or outcoupling optical element 952 maycomprise a layer disposed on the waveguide 940 or may be formed be inthe waveguide 940. For example, a volume holographic or diffractiveoptical element may be formed by changing the index of refraction ofmaterial comprising the waveguide or a layer disposed thereon.Accordingly, the coupling optical element 944 and/or outcoupling opticalelement 952 may be disposed in the volume of the waveguide 940 or alayer disposed thereon. Depending on the design, the coupling opticalelement 944 and/or outcoupling optical element 952 may be transmissiveor reflective and may operate in transmission or reflection. Forexample, the coupling optical element 944 and/or outcoupling opticalelement 952 may include a transmissive or reflective diffractive opticalelement (e.g., grating) or holographical optical element that operatesin transmission or reflection respectively, e.g., turning light via thatis transmitted therethrough or that is reflected therefrom. The couplingoptical element 944 and/or outcoupling optical element 952 can include apolarization optical element, such as a polarization selective turningelement (e.g., polarizer). The polarization selective turning elementmay include one or more polarization gratings, diffractive opticalelements, and/or holographic optical elements and may comprise liquidcrystal structures such as liquid crystal polarization gratings. In someimplementations, the reflective optical element may include a reflector(e.g., mirror). Other elements, such as for example the waveguide 940may be similar to that described above as well.

FIG. 14B illustrates the operation of the imaging system 900 shown inFIG. 14A. Light 970 from the environment is coupled by the couplingoptical element 944 into the waveguide 940. The coupling optical element944 may be configured to turn collimated light at an angle that isgreater than the critical angle of the waveguide 940 such that at leasta portion of this collimated light is guided within the waveguide bytotal internal reflection toward the camera 920. The outcoupling opticalelement 952 can be configured to receive at least a portion of the lightfrom the environment in front of the user that is coupled into thewaveguide 940 via the coupling optical element 944 and guided therein.The outcoupling optical element 952 may be configured to couple theincoupled light out from the waveguide 940 to the camera 920 such thatimages of the environment may be captured by the camera 920. The imagesof the environment may be passed to processing electronics, (e.g., oneor more processors), such as data module 140 (see FIG. 2 ). The datamodule 140 may be configured to reproduce a modified image of theenvironment in an augmented reality context. The processing electronicsmay be in communication with the camera 920 via a wired or wirelesselectronic signal. Additionally or alternatively, the processingelectronics may communicate with the camera 920 using one or more remotereceivers. The processing electronics may reside remotely (e.g., cloudcomputing devices, remote server, etc.).

This imaging system 900 may therefore be used for directly imaging theenvironment, which may be useful for a variety of reasons. For example,imaging the environment can be used to determine where to placeaugmented reality image content with respect to objects in theenvironment. For example, imaging the environment may provide thelocation of a table such that the head mounted display may render animage of person standing next to the table instead of on the table or inthe table. The imaging system 900 described for imaging the environmentmay also be used to image the eye 210, such as is described for FIGS.10, 11A-11E, and/or 12A-12E.

It may be desirable to image a wide view of the environment using theimaging system 900. FIG. 14C schematically illustrates an imaging system900 for collecting light from the environment using a powered opticalelement or lens such as refractive optical element 980 (e.g., a widefield of view lens) forward the eyepiece. The refractive optical element980 may have a positive optical power. The refractive optical element980 (e.g., positive lens) converges collimated light 970 from theenvironment toward the waveguide 940. Other types of lenses than thelens shown in FIG. 14C may be employed. Light that is transmitted (notshown) may pass through a powered optical element or lens such asrefractive optical element 990 (e.g., negative lens) that is configuredfor a negative power equal and opposite of the refractive opticalelement 980. The negative lens 990 may have a similar or the sameoptical power as the positive lens 980 to offset or counter the opticalpower of the positive lens or a portion thereof. In this way, light fromthe environment (e.g., distal of the waveguide 940) may pass through thenegative lens 990, the eyepiece 950, and the positive lens 980 withsubstantially no net change in optical power introduced by these twolenses to the eye. The negative lens 990 may be configured to offset orcounter the optical power of the positive lens 980 such that a user'swill not experience the power of the positive lens when viewing theenvironment in front of the eyepiece 950. The negative lens 990 willalso counter the effect of the positive lens 980 to invert images ofobject in the environment in front of the wearer. Some light 970 fromthe environment may be incoupled into the waveguide 940 by the couplingoptical element 944, in spite of some of the rays of light beingconvergent. The incoupled light incident on the outcoupling opticalelement 952 may be ejected out of the waveguide 940.

Implementations (e.g., those described by FIGS. 14A-14C) may be usedoutside an augmented reality context. For example, it is intended thatan imaging system 900 configured to image the environment be implementedwithin a wearable device, such as, for example, eyeglasses (includingunpowered glasses) or bifocals. Such an imaging system 900 may notrequire an image projector 930 and/or light source 960. Additionally oralternatively, such an imaging system 900 may not require an incouplingoptical element configured for a corresponding image projector 930and/or light source 960.

It may be advantageous to implement such an imaging system 900 forimaging the environment on a viewing screen (e.g., television screen,computer screen), such as a handheld device (e.g., cell phone, tablet).The imaging system 900 could improve video chat capabilities. Forexample, a viewer who is seeing a chat partner look into the screen mayappear to be looking directly at the viewer. This would be possiblesince the light rays captured by the imaging system 900 would becaptured in the same region where the user is looking (e.g., as opposedto viewing a screen but having the light rays captured by a separateoutward-facing camera positioned at a different location).

In implementations where the imaging system 900 of FIG. 14C is also usedto image the eye 210, a light source 960 and/or image projector 930 maybe configured to inject light into the waveguide 940. Because the lightreflected from the eye that is incoupled into the waveguide will passthrough the refractive optical element 990 (e.g., negative lens), apositive powered refractive optical element may be disposed between thelight source 960 and/or image projector 930 and between the waveguide940. The positive lens can be configured to offset or counter anyoptical power provided by the refractive optical element 990 before theincoupled light from the light source and/or light projector is incidenton the eye 210. Other types of lenses than shown in FIG. 14C may be usesas the optical element 990. Alternatively or additionally, processingelectronics in communication with the light source and/or imageprojector can be configured to alter an image sufficient to present tothe user an undistorted image after the light has passed through therefractive optical element 990. Corresponding incoupling opticalelement, outcoupling optical element, and/or coupling optical elementmay be configured to operate on non-collimated light (e.g., divergent,convergent light) in some designs.

In various implementations, the same waveguide 940 may be used to (i)propagate light from the environment in front of the eyepiece 950 andthe user to the camera 940 and (ii) to propagate light from the imageprojector 930 to the eye 210 to form image content therein. Using thesame waveguide 940 may simplify the system and/or the eyepiece and maymake the system and/or eyepiece more compact possibly providing areduced form factor. Reducing the thickness of the eyepiece 950 byreducing the number of waveguide 940 may be advantageous for otherreasons as well. Lower cost and a more simplified manufacturing processmay be some such advantages.

Also in various designs, the same or different imaging system may beused in the same head mounted display to image the eye by propagatinglight from the eye via a waveguide in the eyepiece 950 to the camera 940such as, for example, described above. Such systems may also use theeyepiece to transfer light from an illumination source to the eye 210 toilluminate the eye. In some designs, the eyepiece may additionally beused to propagate light from the image projector 930 to the eye 210 toform image content therein. Using the eyepiece to assist in imaging theenvironment and image the eye (and possibly to illuminate the eye) maysimplify the system and/or may make the system more compact possiblyproviding a reduced form factor.

Moreover, in some implementations, the same waveguide 940 may be used to(i) propagate light from the environment in front of the eyepiece 950 tothe camera 940 and (ii) to propagate light from the eye 210 to thecamera to capture images of the eye. The same waveguide may be used topropagate light from the image projector 930 to the eye 210 to formimage content therein and/or to propagate light from the illuminationsource 960 to the eye 210 to illuminate the eye for image capture. Usingthe same waveguide 940 may simplify the system and/or the eyepiece andmay make the system and/or eyepiece more compact possibly providing areduced form factor. Reducing the thickness of the eyepiece 950 byreducing the number of waveguide 940 may be advantage for other reasonsas well. Lower cost and a more simplified manufacturing process may besome such advantages.

Similarly, in addition to coupling light from the environment into thewaveguide 940, the same coupling optical element 944 may be configuredto direct light from the image projector 930 to the eye 210 to formimage content therein and/or light from the eye into the waveguide 940to be guided therein to the camera 920. Additionally or in thealternative, the same coupling optical element 944 may be configured tocouple light from the illumination source 960 guided within thewaveguide 940 out of the waveguide to the user's eye 210.

As discussed above, one or more of the coupling optical element 944, thein-coupling optical element 942, or the out-coupling optical element 952may comprises polarization selective coupling elements. Accordingly, invarious designs, light input into eyepiece 950 or waveguide 940 ispolarized so as to acted on appropriately by the polarization selectiveturning elements.

Accordingly, in some embodiments the illumination source 960 comprises apolarized light source of suitable polarization to be acted on properlyby the polarization selective coupling/turning elements.

One or more polarization specific optical filters and polarizationmodifying elements may be included in various imaging systems 900, suchas those where the image projector 930 and/or light source 960 aredisposed directly opposite each other through the waveguide 940. Thepolarization sensitive elements may be helpful in reducing directionlight emission into the imaging device 920 and/or to reduce saturationof the imaging device 920, for example, in configurations where theseelements are aligned on opposite sides of the waveguide 940 at the samelateral position. FIGS. 15A-15B show such a configuration. The lightsource 960 such as shown in FIG. 15A can be configured to direct lightthrough a polarization specific optical filter 982 such as a polarizer(e.g., a linear polarizer) and/or through a polarization modifyingelement 986 configured to alter a polarization state of incident light,such as a polarization rotator. A retarder such as a half wave retardermay, for example, rotate linear polarization. Accordingly, anappropriately oriented half wave retarder or half wave plate may rotates-polarized light to p-polarized light or vice versa. Accordingly, invarious implementations, the polarization specific optical filter 982and/or a polarization modifying element 986 are disposed in an opticalpath between the light source 960 and the in-coupling optical element942 so as to provide the properly oriented polarization to thein-coupling optical element. In some implementations, the imaging system900 does not include polarization modifying elements but includesproperly oriented polarization optical filters, such as polarizers.

The light emitted by the light source 960 may pass through anarrangement of optical elements in a particular order. For example, asshown in FIG. 15A, the light may pass first from the light source 960through the polarization specific optical filter 982 (e.g., polarizer)and then through the polarization modifying element 986 (e.g. rotator).After the light has passed through the polarization modifying element986, the light may be incident on an incoupling optical element 942,which may direct the light into the waveguide 940 to be guided therein.

For example, the light source 960 may be configured to emit light of amixed polarization (e.g., s-polarization and p-polarization). Thepolarization specific optical filter 982 may be configured to transmitonly light of a first polarization state (e.g., p-polarization). As thelight continues, the polarization modifying element 986 may beconfigured to change the polarization state of the light (e.g., fromp-polarized to s-polarized). The incoupling optical element may beconfigured to turn s-polarized light into an angle that is greater thanthe critical angle of the waveguide such that the s-polarized light isguided within the waveguide. The incoupled light 904 may besubstantially polarized in the second polarization (s-polarization) asit propagates through the waveguide 940. The coupling optical element944 may be configured to turn light only of the second polarizationstate (s-polarization). The coupling optical element 944 may beconfigured to couple the incoupled light 904 out of the waveguide 940and to the eye 210 to provide illumination for image capture.

In order to prevent direct illumination (e.g., saturation) of theimaging device 920, a polarization modifying element 958 and/or apolarization specific optical filter 984 may be disposed in or on thewaveguide 940 such that only light of a certain polarization state(e.g., p-polarized) can pass through the polarization specific opticalfilter 984 and to the imaging device 920. The polarization modifyingelement 958 (e.g., half waveplate) may be configured to change the stateof the polarization (e.g., from s-polarized to p-polarized). Thepolarization specific optical filter 984 may be configured to transmitonly light of a certain polarization (e.g., p-polarized light)therethrough. In this way, light passing through the polarizationspecific optical filter 982 will not be configured to transmit directlythrough the polarization specific optical filter 984. In any of theimplementations above (e.g., where the image projector 930 and/or thelight source 960 are on the same optical axis as shown in FIG. 15A),such as in FIGS. 10, 11A-11E, and 12A-12E, the configuration of thepolarization specific optical filter 982, the polarization modifyingelement 986, the incoupling optical element 942, the polarizationmodifying element 958, and/or the polarization specific optical filter984 may be implemented according to the design of FIG. 15A. Thepolarization specific optical filter 984 may be atransmissive-reflective polarizer (e.g., a polarizer beam splitter)configured to transmit light of a first polarization and to redirect orreflect light of a second polarization different from the first.

A partially reflective element (e.g., semi-transparent mirror) may beincluded to turn the incoupled light 904 to the imaging device 920. Thepartially reflective element may be disposed between the incouplingoptical element 942 and the polarization modifying element 986 such thata portion of the incoupled light 914 is reflected toward the imagingdevice 920 while reducing leakage of the incoupled light 914 out of thewaveguide 940. The portion of light that does not leak out may be anyfraction between 0 and 1. For example, the portion may be 0.90, where90% of the light rays propagating through the waveguide 940 along thecoupling optical element 944 are maintained within the waveguide 940 ateach reflection of the light rays. Other portions are possible (e.g.,0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or any value in a rangebetween these values).

FIG. 15B illustrates propagation of light reflected or scatter off theretina. Some of the light 910 reflected from the retina that is incidenton the coupling optical element 944 having the second polarization(s-polarization) is turned by the coupling optical element 944 at anglegreater than the critical angle of the waveguide 940 and thus may beguided therein. Some of the light may not be coupled into the waveguide940 and will transmit therethrough as non-incoupled light 912. Theincoupled light 904 may propagate through the waveguide 940 toward thecamera.

Other implementations may benefit from use of polarization selectiveelements proximal the light source and camera. For example, varioussystems can be configured to provide illumination having a firstpolarization and capture images with the camera using light having adifferent polarization. For example, such a configuration may be used toreduce unwanted reflections, such as from the cornea when imaging theretina. Reflecton from the cornea will be specular. Accordingly, iflight of a first polarization is incident on the cornea, the lightreflected from the cornea will retain that first polarization. Incontrast, the retina is diffuse. If light of a first polarization isincident on the retina, the light reflected from the retina does notretain solely the first polarization. The diffuse reflection more likelyresults in unpolarized light. Accordingly, a second polarization,different from the first polarization will be present in the reflectedlight. Likewise by illuminating with a first polarization and imagingwith a second different polarization, the retina can be image withreduced glare from the cornea.

Accordingly, in various implementations, the polarization specificoptical filters 982, 984 may be used together to reduce unwantedreflected light from the eye 210 (e.g., from the cornea). For example,unwanted light, glare, or glint may be reflected off the cornea that maysaturate an image captured by the imaging device 920. Light reflectedfrom the cornea may be specular and maintain its polarization. Bycontrast, light reflected off the retina may be more diffusely reflectedand may be less homogenously polarized. Likewise, a combination ofpolarizers may be used to remove some or most of the unwanted reflectedlight. Initially polarized light can be used for illuminating the eye210. In some designs, a polarized illumination source (e.g., the lightsource 960) may be used. Additionally or alternatively, a firstpolarizer (e.g., the polarization specific optical filter 982) may bepositioned at the beginning of the optical path of the illuminationsource to provide initial polarization of the light. A second polarizer(e.g., the polarization specific optical filter 984) may be positionedat the optical path before the light enters the imaging device 920. Thesecond polarizer may be rotated at 90° from the first polarizer (e.g.the polarizers 982, 984 may be “crossed”). As a result, the eye will beilluminated with the first polarization with some light of the firstpolarization reflected from the cornea. This light will not pass throughthe polarizer 984 proximal the camera. However, light reflected from theretina will include the second polarization. Likewise light diffuselyreflected from the retina will pass through the polarize 984 proximalthe camera and will enable an image of the retina to be captured by thecamera. Thus, in such as configuration unwanted light received from theeye (e.g., from cornea) may be entering the imaging device 920 may bereduced or eliminated. Other configurations are possible. For example, apolarization selective incoupling optical element 942 for coupling lightfrom the light source 960 into the waveguide 940 and a polarizationselective outcoupling optical element for coupling light out of thewaveguide to the camera 920 may be employed having differentpolarization selectivity properties. For example, the polarizationselective incoupling optical element may selectively turn light from theillumination source having a first polarization into the waveguide whilethe outcoupling optical element may selectively turn light of a seconddifferent polarization out of the waveguide to the camera. The effectmay again be to reduce or remove unwanted light received from the eye(e.g., from cornea) before entering the imaging device 920.

Various imaging systems 900 are discussed herein that are capable ofusing the eyepiece 950 to collect light to image the retina. The imagingsystems 900, however, can be configured to image other portions of theeye such as anterior portions of the eye. FIG. 16 illustrates how animaging system 900 can be used for imaging an anterior portion (e.g.,cornea) of an eye 210. The imaging system 900 may include one or moreelements of the example imaging systems 900 described above. Inaddition, an example imaging system 900 may include one or more poweredoptical elements or lenses such as powered refractive optical elements980, 990 having optical power. For example, a positive power lens orpositive lens 980 may be disposed on a proximal side (e.g., closer tothe eye 210) of the eyepiece 950 between the eye 210 and the eyepiece. Anegative power lens or negative lens 990 may be disposed on a distalside of the eyepiece 950, between the eyepiece and the environmentforward the user. One or both of the lenses 980, 990 may be variablefocus elements (e.g., varifocal lenses) and/or may include a liquidcrystal element. In some designs, one or both of the lenses 980, 990includes a Fresnel lens. The lenses 980, 990 may incorporate liquidcrystals to produce Fresnel lens functionality. Such functionality mayallow for variable focus of one or both of the lenses 980, 990. In somedesigns, one or more of the lenses 980, 990 may be integrated withand/or manufactured (e.g., formed) on or into the eyepiece 950.

In various embodiments, the coupling optical element 944 is configuredto turn collimated light reflected from the eye 210 into the light guideto be guided therein. Accordingly, the positive lens 980 may beconfigured to collimate light reflected from the eye 210, such as ananterior portion of the eye (e.g., the cornea). The positive lens 980therefore may have a focal length that is equal or substantially equalto the distance of the lens to the portion of the eye 210 to be imaged,e.g., the cornea.

The negative lens 990 may have a similar or the same optical power asthe positive lens 980 to offset or counter the optical power of thepositive lens. In this way, light from the environment (e.g., distal ofthe waveguide 940) may pass through the negative lens 990, the eyepiece950, and the positive lens 980 with substantially no net change inoptical power introduced by these two lenses. Thus, the negative lens990 may be configured to offset or cancel out the optical power of thepositive lens 980 such that a user will not experience the power of thepositive lens when viewing the environment in front of the eyepiece 950.The negative lens 990 will also counter the effect of the positive lens980 to invert images of object in the environment in front of thewearer.

FIG. 16 illustrates light 928 that is incident on the cornea scatteringtherefrom. The imaging system 900 may be configured to capture thislight 988 reflected from the cornea. For example, the positive lens 980may collect a portion of the light 988 scattered from the cornea andcollimate this light 988. This light 988, collimated by the positivelens 980, is incident on the coupling optical element 944, which isconfigured to turn collimated light into the waveguide 940 at an anglelarger than the critical angle of the waveguide such that the light isguided therein by TIR. The coupling optical element 944, the outcouplingoptical element 952, and/or the waveguide 940 may be as described above.Resultant outcoupled light 906 may be directed by the outcouplingoptical element 952 out of the waveguide 940 to the camera (not shown).

FIG. 16 shows light 928, such as collimated light, which may be from theeyepiece 950 such as describe above. An illumination source 960 maycouple light into the waveguide 940 and the coupling element 944 maycouple this light from the illumination source 960 out of the waveguide.The coupling element 944 may be configured to couple light out of thewaveguide 940 as collimated light. This light illuminates the anteriorportion of the eye (e.g., the cornea) and scatters therefrom. Asdiscussed above, this scattered light 988 can be collected by thepositive lens 980 and the imaging system 900 to form an image of theanterior portion of the eye 210. Also as discussed above, thisillumination 928 directed onto the eye 210 may be invisible (e.g.,infrared) light.

FIG. 16 also shows an alternative arrangement for illuminating the eye210. In some designs, one or more light sources 934 such as LEDs oremitters may be disposed with respect to the eye 210 to direct lightthereon without being guided by TIR through the waveguide 940 anddirected onto the eye 210. In some implementations, the eyepiece 950 orwaveguide 940 is not in an optical path between the one or more lightsource 934 and the eye 210. In some designs, a plurality of such lightsources 934 may be arranged in a pattern (e.g., circular or ring-likepattern) near and/or around the eye. In some designs, the pattern oflight sources 934 may define an illumination axis parallel (e.g.,coaxial) with the optical axis of the one or more lenses 980, 990. Theone or more light sources 934 may be similar to the one or more lightsources 960 described above and may, for example, be pulsed. Similarly,the one or more light sources 934 may comprise infrared light sourcessuch as infrared LEDs or another type of invisible light. Alternatively,the one or more light sources may comprise visible light sources thatemit visible light. Or the one or more light sources may emit bothvisible and invisible (e.g., infrared) light.

FIG. 17 illustrates another example imaging system 900 configured toimage a portion of the eye 210 such as an anterior portion of the eye(e.g., cornea). The imaging system 900 shown in FIG. 17 employs areflective optical element 996 configured to collimate the light fromthe eye, in contrast to the transmissive optical element (lens) 980shown in FIG. 16 . A reflective optical element will have lessaberration than a transmissive optical element as chromatic aberrationis not generally applicable to reflective optical elements such as thereflector 996 shown in FIG. 17 . Accordingly, by using a reflectivesurface in collecting light from the eye 210, less (e.g., chromatic)aberration is introduced in the image captured of the eye.

FIG. 17 illustrates, for example, an imaging system 900 that includes acurved transmissive optical element 996 having a wavelength dependentreflective coating 998. The curved transmissive optical element 996 maybe disposed distal the waveguide 940 (on the environment side of theeyepiece 950). Accordingly, the curved transmissive optical element 996may be disposed between the environment forward the wearer and thewaveguide 940 and/or the coupling optical element 944. Similarly, thewaveguide 940 and/or the coupling optical element 944 may be disposedbetween the curved transmissive optical element 996 and the eye 210.

The wavelength dependent reflective coating 998 may be configured toreflect light of a certain wavelength or range of wavelengths. In someimplementations, for example, the wavelength dependent reflectivecoating 998 may be configured to reflect invisible light (e.g., infraredlight) within a certain range of wavelength, while the wavelengthdependent reflective coating 998 may be configured to transmit visiblelight. The wavelength dependent reflective coating 998 may be disposedon a surface of the curved transmissive optical element 996, in somecases.

As discussed above, in various designs, the coupling optical element 944is configured to turn collimated light reflected from the eye 210 intothe waveguide 940 to be guided therein. Accordingly, the reflectiveoptical element 996 may be configured to collimate light reflected fromthe eye 210, such as an anterior portion of the eye (e.g., the cornea).The curved reflective optical element 996 may therefore have a positiveoptical power for light that is incident on the proximal side thereofthat is reflected from wavelength dependent reflective coating 998. Inparticular, in various designs, the reflective optical element 994 mayhave a focal length that is equal or substantially equal to the distancefrom the reflective optical element 996 to the portion of the eye 210 tobe imaged, e.g., the cornea, iris, etc. Example values of focal lengthsmay be, for example, 2 cm to 8 cm. In some implementations, the focallength is between 4 cm and 6 cm. In some designs, the focal length isabout 5 cm. The focal length may be in any range formed by any of thesevalues or may be outside such ranges in different designs.

In various implementations, the reflective optical element 996 isdisposed on the distal side of the eyepiece 950 forward the eyepiece.Accordingly, the reflective optical element 996 is disposed between theeyepiece 950 and the environment forward the user. Similarly, theeyepiece 950 is disposed between the reflective optical element 996 andthe eye 210.

The curved transmissive optical element 996 may have a curved reflectivesurface having a curvature of any shape. In some implementations, thesurface is rotationally symmetric. In some implementations, the surfacemay be spherical or aspheric (e.g., parabolic). Non-rotationallysymmetric shapes are also possible. In various designs, however, thereflective surface has positive optical power. The reflective opticalelement 996 may comprise, for example, a concave mirror at least forsome wavelengths and/or polarizations.

The curved transmissive optical element 996 may be configured to havenegligible power in transmission. Likewise, the curved transmissiveoptical element 996 may be configured to transmit light withoutintroducing convergence or divergence. In one example, the curvedtransmissive optical element 996 may have a curvature of an inner radiussubstantially the same as a curvature of an outer radius. A thin opticalelment 996 may reduce optical aberration, for example, for lighttransmitted therethrough, may be lighter and/or may be more compact.

In various designs, the reflective optical element 996 comprisesmaterial transmissive to visible light such that the user can see theenvironment in front of wearer. In some cases, to enhance transmission,the curved transmissive optical element 996 may be coated on an outersurface (e.g., the distal surface) with an anti-reflective coating. Theanti-reflective coating may be configured to reduce reflection of, forexample, of visible light such as red, green, and/or blue light. Thereflective optical element 996, however, may be configured to reflect aportion of the light scattered from the eye 210 to form an image of theeye. Accordingly, the reflective optical element 996 may operate ondifferent light differently. For example, the reflective optical element996 may operate on different wavelengths differently. The reflectiveoptical element 996 may be configured to reflect infrared light andtransmit visible light.

As discussed above, one or more light sources 934 may be configured toilluminate the eye 210 with infrared light. Resultant light 988reflected from the eye 210 (e.g., cornea) may be diverge, asschematically illustrated in FIG. 17 . The curved transmissive opticalelement 996 may be disposed to receive this light 988 reflected from theeye (e.g., cornea, iris). The wavelength dependent reflective coating998 may be configured to reflect the light 988 reflected from the eyebecause the wavelength illumination used to illuminate the eye is thesame wavelength that is reflected by the reflective coating on thecurved transmissive optical element 996 (e.g., 850 nm). For example theeye may be illuminated with infrared light (e.g., 850 nm) and the curvedtransmissive optical element 996 may be configured to reflect infraredlight (e.g., 850 nm) and to pass visible light. The shape of the curvedtransmissive optical element 996 may also be configured to collimate thelight 988 reflected from the eye and to reflect the light to thecoupling optical element 944, which turns the collimated light into thewaveguide 940 to be guided therein by TIR.

In FIG. 17 , as in some other designs, one or more light sources 934such as LEDs or emitters may be disposed with respect to the eye 210 todirect light thereon without being guided by TIR through the waveguide940 and directed onto the eye 210. In some implementations, the eyepiece950 or waveguide 940 is not in an optical path between the one or morelight source 934 and the eye 210. In some designs, a plurality of suchlight sources 934 may be arranged in a pattern (e.g., circular orring-like pattern) near and/or around the eye. In some designs, thepattern of light sources 934 may define an illumination axis parallel(e.g., coaxial) with the optical axis of the one or more lenses 980,990. The one or more light sources 934 may be similar to the one or morelight sources 960 described above and may, for example, be pulsed.Similarly, the one or more light sources 934 may comprise infrared lightsources such as infrared LEDs or another type of invisible light. Othertypes of light sources, however, can be used.

FIG. 18 illustrates another example imaging system 900 configured toimage a portion of the eye 210 such as an anterior portion of the eye(e.g., cornea). In the implementation shown in FIG. 18 , polarizationselectivity is employed to assist in controlling the path of the lightreflected from the eye. In particular, in various designs, the couplingoptical element 944 is polarization selective. Light, for example,having a first polarization is transmitted through the coupling opticalelement 944 while light of a second different polarization is turned bythe coupling optical element 944 into the waveguide 940 to be coupledtherein by TIR. Accordingly, in various implementations the eye 210 isilluminated with polarized light or a polarizer (not shown) is disposedbetween the eye and the waveguide 940 such that the light from the eyeincident on the waveguide is polarized. For example, the emitters 934may emit polarized light or a polarizer may be disposed in front of theemitters 934 such that the eye 210 is illuminated with polarized light.Accordingly, in various designs, the polarization of the polarized lightincident and/or reflected from the eye 210 that is received by theoptical coupling element 944 may the first polarization such that saidlight is directed to the reflector 996.

Likewise, in various implementations, the coupling optical element 944(and/or an outcoupling optical element 952) is configured to transmitlight of a first polarization state such as a first linear, circular, orelliptical polarization state (e.g., p-polarization, left handedcircular or elliptical polarization, etc.) and turn light of a secondpolarization state such as a second linear, circular, or elliptical(e.g., s-polarization, right handed circular or elliptical polarization,etc.) into and/or out of the waveguide, respectively. In someimplementations, the eye illuminators 934 may emit only or primarily thefirst polarization (e.g., p polarization) or further include apolarization modifying element (e.g., polarizer) that is configured totransmit only light of the first polarization state (e.g.,p-polarization). Additionally, the coupling optical element 944 and/oroutcoupling optical element 952 may be configured to turn light of asecond polarization (e.g., s-polarization) into and/or out of thewaveguide, respectively.

Similar to the imaging system 900 shown in FIG. 17 , an imaging system900 the curved reflector 998 shown in FIG. 17 comprises a curvedtransmissive optical element 996 having a wavelength dependentreflective coating 998. The wavelength dependent reflective coating 998may be configured to reflect light of a certain wavelength or range ofwavelengths. In some implementations, for example, the wavelengthdependent reflective coating 998 may be configured to reflect invisiblelight (e.g., infrared light) within a certain range of wavelength, whilethe wavelength dependent reflective coating 998 may be configured totransmit visible light. The wavelength dependent reflective coating 998may be disposed on a surface of the curved transmissive optical element996, in some cases.

In various implementations, the curved transmissive optical element 996is disposed on the distal side of the eyepiece 950 forward the eyepiece.Accordingly, the reflective optical element 996 is disposed between theeyepiece 950 and the environment forward the user. Similarly, theeyepiece 950 is disposed between the reflective optical element 996 andthe eye 210.

Accordingly, light having the first polarization (e.g., p-polarization)from the eye 210 is incident on the coupling optical element 944 andpasses therethrough to the curved transmissive optical element 996. Theimaging system 900 further included a polarization modifying opticalelement 978, such as a retarder (e.g., a quarter-wave retarder). Thisretarder 978 is transmissive and imparts a quarter wave of retardance onthe light transmitted therethrough. This light is incident on andreflected from the curved transmissive optical element 996. Thewavelength dependent reflective coating 998 may be configured to reflectthe wavelength of light reflected from the eye. Consequently, this lightis reflected from the curved surface of the curved transmissive opticalelement 996 and is collimated. This collimated light passes againthrough the retarder 978, thereby imparting another quarter wave ofretardance on the light transmitted therethrough. The retardanceintroduced on these two passes through the retarder (e.g., a full waveof retardance) causes the polarization to rotate. Accordingly, the firstpolarization (e.g., p-polarization) transmitted through the polarizationselective coupling optical element 944 on the first pass, is transformedinto the second polarization (s-polarization) and is turned into thewaveguide 940 to be guided to the camera 920 by TIR. As discussed above,in various designs, the coupling optical element 944 is configured toturn collimated light reflected from the eye 210 into the waveguide 940to be guided therein. Accordingly, the reflective optical element 996may be configured to collimate light reflected from the eye 210, such asan anterior portion of the eye (e.g., the cornea). The curved reflectiveoptical element 996 may therefore have a positive optical power. Inparticular, in various designs, the reflective optical element 994 mayhave a focal length that is equal or substantially equal to the distancefrom the reflective optical element 996 to the portion of the eye 210 tobe imaged, e.g., the cornea, iris, etc. Example values of focal lengthsmay be for example, 2 cm to 8 cm. In some implementations, the focallength is between 4 cm and 6 cm. In some designs, the focal length isabout 5 cm.

In various designs, the reflective optical element 996 may comprise acurved surface that is configured to reflect light. The curved surfacemay be spherical or rotationally symmetric in certain cases. Thereflective optical element 996 may comprise, for example, a concavemirror at least for some wavelengths and/or polarizations.

In various designs, the reflective optical element 996 comprisesmaterial transmissive to visible light such that the user can see theenvironment in front of wearer. The wavelength dependent reflectivecoating 998 disposed on a surface of the curved transmissive opticalelement 996 may therefore be transmissive to visible light or at leastcertain wavelength of visible light. The curved transmissive opticalelement 996 may also be coated on an outer surface (e.g., the distalsurface) with an anti-reflective coating. The anti-reflective coatingmay be configured to reduce reflection of red, green, and/or blue light.The reflective optical element 994, however, may be configured toreflect a portion of the light scattered from the eye 210 to form animage of the eye. Accordingly, the reflective optical element 996 mayoperate on different light differently. For example, the reflectiveoptical element 996 may operate on different polarization states (and/orwavelengths) of light differently. The reflective optical element 996may be configured to transmit visible light and reflect infrared light.

As shown in FIG. 17 , the one or more light sources 934 such as LEDs oremitters in FIG. 18 may be disposed with respect to the eye 210 todirect light thereon without being guided by TIR through the waveguide940 and directed onto the eye 210. Accordingly, n some implementations,the eyepiece 950 or waveguide 940 is not in an optical path between theone or more light sources 934 and the eye 210. In some designs, aplurality of such light sources 934 may be arranged in a pattern (e.g.,circular or ring-like pattern) near and/or around the eye. The one ormore light sources 934 may be similar to the one or more light sources960 described above and may, for example, be pulsed. Similarly, the oneor more light sources 934 may comprise infrared light sources such asinfrared LEDs or another type of invisible light. In particular, invarious implementations the light sources 934 may emit light that isreflected by the wavelength dependent reflective coating 998 and/or thecurved transmissive optical element 996. Other types of light sources,however, can be used.

Although the polarization selective coupling optical element 944 isconfigured to be polarization selective depending on the type of linearpolarization incident thereon, other polarization selective couplingoptical elements may be polarization selective to other types ofpolarization states such as different types of circular or ellipticalpolarization. The polarization selective coupling optical element 944may, for example, be configured such that the first polarization, suchas a first circular or elliptical polarization (e.g., left handedpolarization or LHP-polarization), is transmitted through thepolarization selective coupling optical element 944 and the secondpolarization, such as second circular or elliptical polarization (e.g.,right handed polarization or RHP), is turned into the light guide, orvice versa. Such a polarization selective coupling optical element 944may comprise liquid crystal such as cholesteric liquid crystal. Examplesof some liquid crystal optical elements are discussed below in thesection titled “Cholesteric Liquid Crystal Mirror,” in U.S. PublicationNo. 2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERICLIQUID CRYSTAL,” filed on Dec. 7, 2017; in U.S. Publication No.2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWER REFLECTOR,”filed on Feb. 22, 2018; in U.S. Publication No. 2018/0239177, titled“VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATION CONVERSION,”filed on Feb. 22, 2018; each of which is hereby incorporated byreference in its entirety and for all purposes.

A polarization modification element or retarder such as a circularpolarizer may be disposed between the eye and the polarization selectivecoupling optical element 944 to convert the light reflected from the eyeto the first polarization (e.g., LHP). The LHP light will pass throughthe polarization selective coupling optical element 944, reflect fromthe reflector 998, change polarization into RHP and be turned by thepolarization selective coupling optical element 944 into the waveguideto the camera.

In some implementations, the reflector 996 may be polarization selectivein its reflectivity such that only light of a certain polarization stateis reflected and/or that light of a different polarization state istransmitted. Such an optical element may comprise liquid crystal such ascholesteric liquid crystal. Examples of such optical elements arediscussed below in the section titled “Cholesteric Liquid CrystalMirror,” in U.S. Publication No. 2018/0164627, titled “DIFFRACTIVEDEVICES BASED ON CHOLESTERIC LIQUID CRYSTAL,” filed on Dec. 7, 2017; inU.S. Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLEPOWER REFLECTOR,” filed on Feb. 22, 2018; in U.S. Publication No.2018/0239177, titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ONPOLARIZATION CONVERSION,” filed on Feb. 22, 2018; each of which ishereby incorporated by reference in its entirety and for all purposes.Such optical elements may reflect light of a first polarization statesuch as a first circular or elliptical polarization state (left handedcircular or elliptical polarization) and transmit light of a secondpolarization state such as a second circular or elliptical polarizationstate (e.g. right handed circular or elliptical polarization) or viceversa. In some embodiments, the liquid crystal is disposed on a curvedsurface of the reflector 996 such that in reflection, the reflector hasoptical power such as positive optical power. In various otherimplementations, the liquid crystal optical element may be flat orplanar. For example, the liquid crystal may be disposed on a flat orplanar substrate or layer. Despite being flat, optical power may beincluded in the liquid crystal optical element. Such an element may bereferred to as a cholesteric liquid crystal reflective lens.Accordingly, light from the eye may be collimated and reflected to thecoupling optical element 998. The reflector, for example, may reflectlight of a first polarization state (e.g., left handed circular orelliptical) and transmit light of a second polarization (e.g., righthanded circular or elliptical polarization). Accordingly, the eye 210 isilluminated with left handed circular polarized light or the lightreflected from the eye is transmitted through a polarizer (e.g., acircular or elliptical polarizer) that transmits light having the firstpolarization (e.g., left handed circular or elliptical polarized light).The coupling optical element 944 may also be polarization selective andmay transmit LHP light and turn RHP light into the waveguide. The LHPlight from the eye passes through the coupling optical element 944. Thistransmitted LHP light also is incident on the wavelength-selectiveliquid crystal reflector 996 and reflected therefrom. In certaindesigns, the wavelength-selective liquid crystal reflector 996transforms the first polarization state (e.g. LHP) into the secondpolarization state (e.g. RHP) upon reflection. This light of the secondpolarization state (e.g., RHP light) is directed to the coupling opticalelement 944, which turns light of the second polarization state (RHP)into the waveguide 940 to the camera 920.

In some designs, the coupling optical element 944 does not comprise aliquid crystal grating but instead comprises, for example a surfacerelief diffraction grating or holographic grating. As discussed above,these coupling optical element 944 that do not comprise cholestericliquid crystal may also comprise a volume diffractive or holographicoptical elements or grating.

Accordingly, light scattered from the eye, is reflected by thereflective optical element 996 back to the waveguide 940 for couplinginto the waveguide by the coupling element 944. In contrast, however, aportion of the unpolarized light from the environment in front of thewearer corresponding to the second polarization state (e.g., RHP) wouldbe transmitted through the reflective optical element 996. Thus, thewearer could see objects through the reflective optical element 996.

In various designs, however, the reflective optical element 996 wouldhave negligible power in transmission. For example, the reflectiveoptical element 996 may have curved surfaces on both sides of theoptical element having the same curvature such that the aggregate powerof the optical element for light transmitted therethrough would benegligible.

As discussed above, in various implementations, the reflective opticalelement 996 comprises a cholesteric liquid crystal reflective lens, acholesteric liquid crystal reflective element such as discussed below inthe section titled “Cholesteric Liquid Crystal Mirror,” in U.S.Publication No. 2018/0164627, titled “DIFFRACTIVE DEVICES BASED ONCHOLESTERIC LIQUID CRYSTAL,” filed on Dec. 7, 2017; in U.S. PublicationNo. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWER REFLECTOR,”filed on Feb. 22, 2018; in U.S. Publication No. 2018/0239177, titled“VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATION CONVERSION,”filed on Feb. 22, 2018; each of which is hereby incorporated byreference in its entirety and for all purposes. Such optical element mayoperate on a particular wavelength or wavelength range. Accordingly,light such as infrared light reflected from the eye may be acted on bythe cholesteric liquid crystal reflective element. However, light not inthat wavelength range such as visible light from the environment may bepassed through the cholesteric liquid crystal reflective element withoutbeing operated on by the cholesteric liquid crystal reflective element.Accordingly, the cholesteric liquid crystal reflective element may havenegligible power for this visible light from the environment passingtherethrough

As discussed above, in certain implementations, the illumination source960 couples light into the waveguide 940 that is turned out of thewaveguide to illuminate the eye 210. In such embodiments, the couplingoptical element 944 may be polarization selective. For example, thecoupling optical element 944 may transmit a first polarization(p-polarization) and transmit a second polarization (s-polarization).

Accordingly, if light from the illumination source 906 propagatesthrough the waveguide 940 and is turned by the coupling optical element944, this illumination will be s-polarization. A polarization modifyingoptical element (e.g., a quarter wave retarder) may be disposed betweenthe waveguide 940 and the eye 210 so as to cause rotation of thepolarized light reflected from the eye. Light from the light source 960that is reflected from the eye 210 will pass twice through the quarterwave retarder and as a result the s-polarized light ejected from thewaveguide by the coupling element 944 to illuminate the eye will betransformed into p-polarized light.

This p-polarized light will be transmitted through the coupling opticalelement 944 and the waveguide and be incident on the reflective opticalelement 996.

The imaging system 900 may further comprise a second polarizationmodifying element 978 which may comprise, for example, a retarder orwaveplate as discussed above. This retarder may comprise for example aquarter wave retarder. The second polarization modifying element 978 maybe disposed distal of the waveguide 940, between the waveguide and thereflector 996. The second polarization modifying element 978 may also bedisposed between the coupling element light 944 and the reflector 996.Light (p-polarized) from the eye 210 that is transmitted through thecoupling element light 944 passes through second polarization modifyingelement 978 is transformed into circular polarization. If the reflector996 reflects circular polarized light, this light will be reflected backto the waveguide 940 after passing again through the polarizationmodifying element 978. Two passes through this polarization modifyingelement (e.g., quarter wave retarder) 978 will cause the light to betransformed into s-polarized light, which will be turned by the couplingelement 944 into the waveguide to be guide therein to the camera (notshown).

As illustrated in FIG. 18 , the light 988 reflected from the eye 210 isdiverging. This light is incident on the reflector 996, which is curvedor otherwise has positive optical power, and may be collimated thereby.The coupling optical element 944, which is configured to turn collimatedinto the waveguide 940, will therefore direct this collimated light fromthe curved reflective optical element 996 toward the imaging device 920(not shown). Accordingly, the light reflected from the eye 210 that iscollimated by the curved reflective optical element 996 is coupled intothe waveguide 940 and guided therein toward the outcoupling opticalelement 952. The outcoupling optical element 952 may be configured todirect the light out of the eyepiece 950 to the camera (not shown).

A wide variety of variations are possible in the configurations of theimaging system. Different types of reflectors 996 and coupling elements944 may be employed. The reflectors 996 and coupling elements 944 may,for example, be configured to operate on linear polarized light orcircular or elliptical polarized light. As discussed, the reflectors 996have optical power. The reflectors 996 and coupling elements 944 maycomprise cholesteric liquid crystal grating reflectors and/or lenseswith our without optical power. Polarization modifying elements 978 suchas retarders may be included between the coupling elements 944 and thereflector and/or between the coupling elements 944 and the eye. In someembodiments, a polarizer such as a circular polarizer or a linearpolarizer may be disposed between the eye and the coupling elements 944.If for example unpolarized light is reflected from the eye, a polarizer(e.g., circular polarizer or linear polarizer) may be disposed betweenthe eye and the coupling elements 944. In some such cases the couplingelements 944 are polarization selective.

In configurations such as shown in FIGS. 17 and 18 , where lightreflected from the eye passes through the waveguide 940 to the curvedreflective optical element 996 to be collimated and redirected back tothe waveguide, background noise is introduced. This background noiseresults from light passing initially from the eye through the couplingoptical element 944. As discussed above, the coupling optical element944 may be configured to turn collimated light into the waveguide 940 tobe guided therein to the camera 920 where an image is formed. Thecoupling optical element 944 will, however, turn some non-collimatedlight incident thereon. Accordingly, on the initial pass through thecoupling optical element 944 and the waveguide 940 to the curvedreflective optical element 996, some of the non-collimated (diverging)light reflected from the eye will be coupled by the coupling opticalelement 944 into the waveguide and contribute background noise to imageof the eye formed at by the camera 920. This noise will be superimposedon the image formed by the collimated light retro-reflected by thecurved reflective optical element 996 that is coupled by the couplingoptical element 944 into the waveguide to be guided therein to thecamera 920.

In certain designs, this noise can be subtracted out from the image. Theprocess for subtracting out the noise from the signal may involve (a)measuring the amount of light coupled by the coupling optical element944 on the initial pass through the coupling optical element 944 to thecurved reflective optical element 996 that is turned and reaches thecamera 920 (referred to as N) and (b) measuring the total signal at thecamera 920 when light passes through coupling optical element 944 andthe waveguide 940 to the curved reflective optical element 996, iscollimated, and reflected back to the coupling optical element andturned to the camera. This total signal will also include some noise, N,as the uncollimated light reflected from the eye will have passedthrough the coupling optical element 944 to get to the curved reflectiveoptical element 996 and thus some of uncollimated light will be turnedby the coupling optical element 944 to the camera 920. If the noise, N,can be measured separately from the total signal, T, that includes thenoise superimposed over the image of the eye, the noise, N, can besubtracted out from the total signal, T, as represented by the formulabelow:I=T−N

where I represents the image with the noise component, N, removed.

The two measurements (a) and (b) above can be obtained in various ways.For example, as shown in FIG. 19 , a shutter 936 can be disposed betweenthe curved reflective optical element 996 and the waveguide 940 andcoupling optical element 944. This shutter 936 may be configured toblock light when the shutter is in a first state and to transmit lightwhen the shutter is in a second state. This shutter 936 may comprise,for example, a liquid crystal shutter.

Accordingly, the noise component N can be measured when the shutter 936is in the first state where light reflected from the eye 210 is incidenton the coupling optical element 944, passes therethrough toward thecurved reflective optical element 996, however, is prevented fromreaching the curved reflective optical element by the closed shutter. Asdiscussed above, some of the light reflected from the eye 210, althoughmainly uncollimated, does couple into the coupling optical element 944and is turned into the waveguide and guided therein to the camera 920.As referenced above, this light does not contribute to formation of animage, but will be background noise. The camera 920 may record thisnoise, N, when the shutter 936 is closed.

The total signal, T, including both the noise, N, and the image, can bemeasured when the shutter 936 is in the second state where the shutteris open. Light reflected from the eye 210 is again incident on thecoupling optical element 944. Some of this light reflected from the eye210, although mainly uncollimated, couples into the coupling opticalelement 944 and is turned into the waveguide and guided therein to thecamera 920. Most of this light reflected from the eye 210, however,passes through the coupling optical element 944, through the openshutter 936 and to the curved reflective optical element 996. The curvedreflective optical element 996 collimates and reflects at least aportion of this light back to the coupling optical element 944, whichturns this collimated light into the waveguide 920 to be guided to thecamera 920 to form an image of the eye 210. The camera 920 can capturethis image of the eye 210.

Processing electronics (such as processing electronics 140) incommunication with the camera 920 can receive the noise component, N,measured when the shutter 936 was in the first closed state as well asthe total signal, T, measured when the shutter was in the second openstate and can subtract the two (T-N). In this manner, the noise, N,contributed by the non-collimated light reflected from the eye 210 thatis coupled into the coupling optical element 944 on the initial passtherethrough, can be subtracted from the total image signal, T. Theprocessing electronics may be in communication with the camera 920 via awired electronic signal. Additionally or alternatively, the processingelectronics may communicate with the camera 920 using one or more remotereceivers. The processing electronics may reside remotely (e.g., cloudcomputing devices, remote server, etc.).

Other ways may be employed to perform the measurement of (a) and (b) toobtain N and T and subtract N from T. For example, if the curvedreflective optical element 996 is wavelength selective such as shown inFIG. 18 , the eye can be illuminated with light of different wavelengthat different times. For example, to perform the measurement (a) andquantify the noise, N, the eye can be illuminated with a wavelength thatis not reflected by the curved reflective optical element 996. However,to perform the measurement (b) and quantify the total signal, T, the eyecan be illuminated with a wavelength that is reflected by the curvedreflective optical element 996. The noise, N, can then be subtractedfrom the total T, as discussed above (e.g., T-N).

FIGS. 20-20E illustrate an example imaging system 900 configured to usewavelength modulation to measure and subtract out the noise component,N, as discussed above. The imaging system 900 in FIGS. 20A-20E includesa curved transmissive optical element 996 that is wavelength selective(such as described with reference to FIGS. 17 and 18 above). Forexample, the curved transmissive optical element 996 has a wavelengthdependent reflective coating 998 on a curved surface thereof. Theimaging system 900 may also include one or more light sources orillumination sources (not shown) configured to illuminate the eye 210.The one or more light sources may be configured to emit infrared light.The one or more light sources, however, can be configured to emitdifferent color or wavelength light at different times. Such wavelengthmodulation can enable the measurement of N separately so as to besubtracted out from the total signal, T.

In various implementations, for example, the one or more illuminationsources 960, 934 may be configured in a first state to emit one or morewavelengths that are reflected by the curved reflective optical element,λ_(Reflect), and in a second state one or more wavelengths that are notreflected λ_(Not Reflect). In the second state, no more than negligibleamounts of wavelengths that are reflected by the curved reflectiveoptical element, λ_(Reflect), are emitted. Similarly, in the firststate, no more than negligible amounts of wavelengths that are notreflected λ_(Not Reflect) are emitted.

In some examples, the reflected wavelength(s), λ_(Reflect), may bebetween about 800 nm and 950 nm. The reflected wavelength(s),λ_(Reflect), may be between about 835 nm and 915 nm. The reflectedwavelength(s), λ_(Reflect), may be between about 840 nm and 870 nm. Insome designs, the reflected wavelength, λ_(Reflect), is about 850 nm.The light emission 928 from the one or more light sources 960 mayilluminate the eye.

As shown in FIG. 20B, light 988 having the wavelength(s) that are notreflected by the curved reflective optical element 944, λ_(Not Reflect),(and no more than negligible amounts of light that is reflected by thecurved reflective optical element 944, λ_(Reflect)) is reflected offpart of the eye 210 (e.g., the cornea). Because this light compriseswavelength(s) that are not reflected by the curved reflective opticalelement 944, λ_(Not Reflect), rays of light 916 are shown propagatingthrough the curved reflective optical element 996 to the environmentforward the user.

Although the light 988 incident on the coupling optical element 944 isnot collimated, the coupling optical element nevertheless couples atleast some light 914 into the waveguide 940 to be guided to the camera920. According, the camera 920 may capture an image (Image #1)corresponding to the noise component, N, that results from uncollimatedlight that is turned by the coupling optical element 944 on the initialpass to the curved reflective optical element 996. This image (Image #1)is background noise and does is not a recognizable image of the eye.Processing electronics 140 is shown as receiving this first image (Image#1).

In FIGS. 20C-20E, the illumination sources (not shown) emit one or morewavelengths that are reflected by the curved reflective optical element,λ_(Reflect), and no more than negligible amounts of wavelengths that arenot reflected λ_(Not Reflect). This wavelength, λ_(Reflect), may be, forexample, 850 nm.

As shown in FIG. 20C, some of the light 988 reflected from the eye 210that is incident on coupling optical element 944 in the first passthrough the coupling optical element 944 is coupled by the couplingoptical element 944 into the waveguide 940 (as in FIG. 20B) and directedtoward the camera 920. Additionally, the curved transmissive opticalelement 996, which selectively reflect light of wavelength λ_(Reflect),reflects and collimates the non-incoupled light 918 reflected from theeye 210 that is incident on the curved transmissive optical element. Asillustrated in FIG. 20E, the coupling optical element 944 turns andcouples this collimated reflected light into the waveguide 940 towardthe camera 920. FIG. 20E shows both components reaching the camera 920,light 988 reflected from the eye 210 that is incident on couplingoptical element 944 in the first pass through the coupling opticalelement 944 is coupled by the coupling optical element into thewaveguide 940 and light reflected and collimate by the curvedtransmissive optical element 996 that is coupled by the coupling opticalelement into the waveguide. The camera 920 may capture an image (Image#2) corresponding to this total image component, T. Processingelectronics 140 is shown as receiving this second image (Image #2).

As discussed above, the processing electronics may subtract the noisefrom the image, T-N. In this example, Image #1 can be subtracted fromImage #2. Accordingly, the processing electronics 140 may be configuredto modify the second image based on the first image. Other approaches,however, are possible. For example, the processing electronics 140 maybe configured to create a new image that represents a version of thesecond image with reduced optical noise. Implementations for subtractingnoise from the image may be used in implementations described above. Forexample, implementations shown in FIGS. 10, 11A-11E, and/or FIGS.12A-12E can include a shutter 936 and/or a curved transmissive opticalelement 996 having a wavelength dependent reflective coating 998configured to selectively reflect non-incoupled light 912 and to directthe light to an imaging device 920.

As discussed above, the Image #1 was obtained for the case where thelight was illuminated with one or more wavelengths that are notreflected by the curved reflective optical element, λ_(Not Reflect), andno more than negligible amounts of wavelengths that are reflectedλ_(Reflect). Image #2 was obtained for the case where the light wasilluminated with one or more wavelengths that are reflected by thecurved reflective optical element, λ_(Reflect), and no more thannegligible amounts of wavelengths that are not reflectedλ_(Not Reflect). Accordingly, the one or more illumination sources 960,934 may be configured to modulate in wavelength. For example, in certaindesigns the one or more illumination sources 960, 934 may comprise afirst illumination source configured to output one or more wavelengthsnot reflected by the curved reflective optical element, λ_(Not Reflect),and no more than negligible amounts of wavelengths that are reflectedλ_(Reflect). The one or more illumination sources may further comprise asecond illumination source configured to output one or more wavelengthsthat are reflected by the curved reflective optical element,λ_(Reflect), and no more than negligible amounts of wavelengths that arenot reflected λ_(Not Reflect). The intensity of the first and secondillumination sources can be alternately increased and decreased, turnedon and off, attenuated and not attenuated, passed and blocked to providemodulation in the wavelength of light illuminating the eye. For example,during a first time interval the first illumination source can beblocked while the second illumination source is not blocked. During asubsequent second time interval, the second illumination source can beblocked while the first illumination source is not blocked. This processcan be repeated to provide modulation of the wavelength of lightilluminating the eye. In other designs, the wavelength of a light sourcemay be tuned and detuned to shifted the wavelength back and forthbetween λ_(Reflect) and λ_(Not Reflect). Other arrangements arepossible.

As described above, imaging systems 900 may be included in head mounteddisplays such as augmented reality displays that additionally providethe ability to image the eye by collecting light with the eyepiece 950.Such imaging systems 900 may be used for eye tracking. Multiple imagesof the retina or an anterior portion of the eye may be obtained.Movement and/or repositioning of the eye can be ascertained from theseimages to track the eye position and/or orientation. These imagingsystem may also be use as for biometric imaging and/or for identifyingthe user. For example, an image of the user's eye such as of the retinaor iris may be obtained and recorded. A subsequent image of the eye(e.g., retina, or iris) of the wearer may be obtained at a later time.The two images may be compared to determine whether the wearer in thatlater instance was the wearer in the first instance. Other uses for theimaging systems however are possible.

Although illumination systems may be described above as waveguide basedand comprising one or more waveguides, other types of light turningoptical elements may be employed instead of a waveguide. Such lightturning optical elements may include turning features to eject the lightout of the light turning optical element, for example, onto the spatiallight modulator. Accordingly, in any of the examples described herein aswell as any of the examples below, any reference to waveguide may bereplaced with light turning optical element instead of a waveguide. Sucha light turning optical element may comprise, for example, a polarizingbeam splitter such as a polarizing beam splitting prism.

As discussed above the systems described herein can allow for collectionof biometric data and/or biometric identification. For example, the eyeor portions thereof (e.g., the retina) can be imaged to provide suchbiometric data and/or biometric identification. Images of the eye suchas of the retina may be obtained at various times when the head mounteddisplay system is being worn by a user, presumably the same user. Acollection of such images can be recorded, for example, in a database.These images may be analyzed to collect biometric data. Such biometricdata may be useful for monitoring the user's health or medical status.Different medical parameters can be monitored by imaging the patient,for example, the patient eye (e.g., retina). The medical parameters canbe recorded and compared with subsequent measurements obtained when theuser is wearing the head mounted display system.

In addition, if a person begins wearing the head mounted display systemand an image of the user's eye is captured that does not match theimages stored in the database a conclusion may be drawn that the personcurrently wearing the head mounted display system is different from theprevious user. This can be useful in determining whether the intendeduser is wearing the headset or if it is being worn by a new user. Such afeature may allow for certain medical, security, and/orconvenience-in-use applications or functionality. For example, the headmounted display may be configured to identify a wearer based oncharacteristics of the wearer's eye. For example, the system can beconfigured to determine an individual based on features of a wearer'sretina (e.g. blood vessels), cornea, or other eye features. In someimplementations for example, a series of markers may be determined for aparticular wearer. Based on the series of markers, the system may beable to determine that the previous user is wearing the headset or,alternatively, that another user is wearing the headset. The markers mayinclude a shape or center of a user's cornea, a configuration of bloodvessels in the user's retina, an intensity and/or position of areflection of light from the cornea, a shape of an aspect of the eye,and/or any other biometric marker. In certain implementations aconfusion matrix can be determined. As discussed above for example inthe discussion of developing a retinal map using a virtual/fixationtarget at a variety of location (see, e.g., FIG. 13B), the system mayhave a user look in a set of pre-determined directions or eye poses anddevelop a matrix of characteristics of the eye or part of the eye (e.g.,cornea, retina, etc.) associated with each direction or eye pose. Usingsuch a matrix, the system can determine an identity of the individual.Other methods are possible.

Similarly, as discussed above, a wide variety of configurations of thesystem are possible. For example, FIG. 21 shows an example eyepiece 900that can be used to simultaneously project light into a user's eye whileimaging the user's eye. The eyepiece 900 shown includes an incouplingoptical element 2104, a light distributing element 2108, and a lightconsolidating element 2116, and an outcoupling optical element 2120 onopposite sides of a coupling optical element 2112. Each of these opticalelements may be disposed within or on a waveguide 2102. The waveguide2102 may correspond, for example, to one of the waveguides 670, 680, 690described herein (see, e.g., FIG. 9A-9C). The incoupling optical element2104 may correspond to one of incoupling optical elements 700, 710, 720described herein and/or to the incoupling optical element 942 (see,e.g., FIG. 10 ) and may be configured to inject image content from aprojector into the waveguide and/or illumination from a light source960. The light distributing element 2108 may correspond to one of thelight distributing elements 730, 740, 750 described herein (see, e.g.,FIGS. 9A-9C and may be used to spread light in a given direction andredirect the light from the incoupling optical element 2104 to thecoupling optical element 2112. The coupling optical element 2112 maycorrespond to the coupling optical element 944 described herein (see,e.g., FIG. 10 ). In some designs, the coupling optical element 2112includes functionality described herein with respect to the outcouplingoptical elements 800, 810, 820 (see FIGS. 9A-9C). The lightconsolidating element 2116 may be configured to reduce the lateralspatial extent of light received from the coupling optical element 2112and redirect said light toward the outcoupling optical element 2120. Theoutcoupling optical element 2120 may correspond to the outcouplingoptical element 952 described herein (see, e.g., FIG. 10 ).

The incoupling optical element 2104 may be disposed within or on thewaveguide 2102 so as to receive light, such as from a projector (e.g.,the image projector 930) and/or an illuminator (e.g., the light source960). The light may be passed via the waveguide 2102 to the associatedlight distributing optical element 2108. Any of the incoupling opticalelement 2104, light distributed optical element 2108 or coupling opticalelement 2112 may be disposed on a major surface of (e.g., on a top orbottom surface) of the waveguide or within the waveguide. Similarly, anyone or combination of the light consolidating element 2116, and/or theoutcoupling optical element 2120 may be disposed on the major surface(e.g., a top or both major surface) of the waveguide 2102 or within thewaveguide.

The coupling optical element 2112 may receive the light (e.g., via TIR)from the light distributing element 2108 and expand the light to enterthe user's eye. Thus, the coupling optical element 2112 may be disposedin front of a user's eye and project image content therein. Additionallyor alternatively, the coupling optical element 2112 may be configured toprovide illuminating light onto and/or into the user's eye.

Light that is reflected from the eye (e.g., the illumination light fromthe illumination source) may be reflected and captured by the couplingoptical element 2112. Thus, in some embodiments, the coupling opticalelement 2112 can serve to both outcouple light received from the lightdistributing element 2108 and incouple light received from the eye intothe waveguide 2102.

In some embodiments, the coupling optical element 2112 may include oneor more diffractive optical elements (DOEs) such that the couplingoptical element 2112 has dual functionality. A first DOE (e.g., agrating, holographic region) may be configured to outcouple light aswell and a second DOE may be configured to incouple reflected light fromthe eye into the waveguide 2102. In some embodiments, both the first andsecond DOEs are superimposed (e.g., occupy the same or approximately thesame volume) within the waveguide 2102.

Alternatively, in some embodiments, the coupling optical element 2112includes at least two DOEs that are stacked on over or in front of theother. For example, with reference to FIG. 21 , the first DOE of thecoupling optical element 2112 may be disposed over, whereas the seconddiffractive element may be disposed under the first DOE. The order ofeach DOE may be reversed in other implementations.

Cholesteric Liquid Crystal Mirror

Some liquid crystals are in a phase referred to as a chiral phase or acholesteric phase. In a cholesteric phase, the liquid crystals canexhibit a twisting of the molecules along an axis perpendicular to thedirector, where the molecular axis is parallel to the director. Asdescribed herein, a cholesteric liquid crystal (CLC) layer comprises aplurality of liquid crystal molecules in a cholesteric phase that extendin a direction, e.g., a direction perpendicular to the director such asa layer depth direction, and that are successively rotated or twisted ina rotation direction, e.g., clockwise or counterclockwise. The directorsof the liquid crystal molecules in a chiral structure can becharacterized as a helix having a helical pitch (p), which correspondsto a length in the layer depth direction corresponding to a net rotationangle of the liquid crystal molecules of the chiral structures by onefull rotation in the first rotation direction. In other words, thehelical pitch refers to the distance over which the liquid crystalmolecules undergo a full 360° twist. The liquid crystals displayingchirality can also be described as having a twist angle, or a rotationangle (ϕ), which can refer to, for example, the relative azimuthalangular rotation between successive liquid crystal molecules in thelayer normal direction, and as having a net twist angle, or a netrotation angle, which can refer to, for example, the relative azimuthalangular rotation between an uppermost liquid crystal molecule and alowermost liquid crystal molecule across a specified length, e.g., thelength of a chiral structure or the thickness of the liquid crystallayer. As described herein, a chiral structure refers to a plurality ofliquid crystal molecules in a cholesteric phase that extend in adirection, e.g., a direction perpendicular to the director such as alayer depth direction, and are successively rotated or twisted in arotation direction, e.g., clockwise or counterclockwise. In one aspect,the directors of the liquid crystal molecules in a chiral structure canbe characterized as a helix having a helical pitch.

FIG. 22 illustrates a cross-sectional side view of a cholesteric liquidcrystal (CLC) layer 1004 comprising a plurality of uniform chiralstructures, according to embodiments. In the CLC layer 1004, the chiralstructures that are adjacent in a lateral direction, e.g., x-direction,have similarly arranged liquid crystal molecules. In the illustratedembodiment, the chiral structures 1012-1, 1012-2, . . . 1012-i aresimilarly configured such that liquid crystal molecules of the differentchiral structures that are at about the same depth, e.g., the liquidcrystal molecules closest to the light-incident surface 1004S, have thesame rotation angle, as well as successive rotation angles of successiveliquid crystal molecules at about the same depth, as well as the netrotation angle of the liquid crystal molecules of each chiral structure.

The CLC 1004 comprises a CLC layer 1008 comprising liquid crystalmolecules arranged as a plurality of chiral structures 1012-1, 1012-2, .. . 1012-i, wherein each chiral structure comprises a plurality ofliquid crystal molecules, where i is any suitable integer greater than2. In operation, when incident light having a combination of light beamshaving left-handed circular polarization and light beams havingright-handed circular polarization are incident on the surface 1004S ofthe CLC layer 1008, by Bragg-reflection, light with one of the circularpolarization handedness is reflected by the CLC layer 1004, while lightwith the opposite polarization handedness is transmitted through the CLClayer 1008 without substantial interference. As described herein andthroughout the disclosure, the handedness is defined as viewed in thedirection of propagation. According to embodiments, when the directionof polarization, or handedness of the polarization, of the light beams1016-L, 1016-R is matched such that it and has the same direction ofrotation as the liquid crystal molecules of the chiral structures1012-1, 1012-2, . . . 1012-i, the incident light is reflected. Asillustrated, incident on the surface 1004S are light beams 1016-L havingleft-handed circular polarization and light beams 1016-R having aright-handed circular polarization. In the illustrated embodiment, theliquid crystal molecules of the chiral structures 1012-1, 1012-2, . . .1012-i are rotated in a clockwise direction successively in thedirection in which incident light beams 1016-L, 1016-R travel, i.e.,positive x-direction, which is the same rotation direction as the lightteams 1016-R having right-handed circular polarization. As a result, thelight beams 1016-R having right-handed circular polarization aresubstantially reflected, whereas the light beams 1016-L havingleft-handed circular polarization are substantially transmitted throughthe CLC layer 1004.

As described supra, by matching the handedness of polarization ofincident elliptically or circularly polarized light with the directionof rotation as the liquid crystal molecules of the chiral structures ofa CLC layer, the CLC layer can be configured as a Bragg reflector.Furthermore, one or more CLC layers having different helical pitches canbe configured as a wave-length selective Bragg reflector with highbandwidth. Based on the concepts described herein with respect tovarious embodiments, the CLC layers can be configured as an off-axis oron-axis mirror configured to selectively reflect a first range ofwavelengths, for example, infrared wavelengths (e.g., the nearinfrared), while transmitting another range of wavelengths, e.g.,visible wavelengths.

FIG. 23 illustrates an example of an eye-tracking system 2300 employinga cholesteric liquid crystal reflector (CLCR), e.g., awavelength-selective CLCR 1150 configured to image an eye 302 of aviewer, according to various embodiments. Unlike the CLC layer 1004described above with respect to FIG. 22 , the chiral structures in thewavelength-selective CLCR 1150 that are adjacent in a lateral direction,e.g., x-direction, have differently arranged liquid crystal molecules.That is, the chiral structures are configured such that liquid crystalmolecules of the different chiral structures that are at about the samedepth, e.g., the liquid crystal molecules closest to the light-incidentsurface 1004S, have different rotation angle. As a result, lightincident on the CLCR 1150 is reflected at an angle (OR) relative to thelayer depth direction, as described further below in the context of theeye-tracking system 2300.

Eye tracking can be a useful feature in interactive vision or controlsystems including wearable display systems described elsewhere in thespecification, for virtual/augmented/mixed reality display applications,among other applications. To achieve effective eye tracking, it maydesirable to obtain images of the eye 302 at low perspective angles, forwhich it may in turn be desirable to dispose an eye-tracking camera 702b near a central position of viewer's eyes. However, such position ofthe camera 702 b may interfere with user's view. Alternatively, theeye-tracking camera 702 b may be disposed to a lower position or a side.However, such position of the camera may increase the difficulty ofobtaining robust and accurate eye tracking since the eye images arecaptured at a steeper angle. By configuring the CLCR 1150 to selectivelyreflect infrared (IR) light 2308 (e.g., having a wavelength of 850 nm)from the eye 302 while transmitting visible light 2304 from the world,the camera 702 b can be placed away from the user's view while capturingeye images at normal or low perspective angles. Such configuration doesnot interfere with user's view since visible light is not reflected. Thesame CLCR 1150 can also be configured as an IR illumination source 2320by reflecting IR light from an IR source, e.g., IR LED, into the eye302, as illustrated. A low perspective angle of IR illuminator canresults in less occlusions, e.g., from eye lashes, which configurationallows more robust detection of specular reflections, which can beuseful feature in modern eye-tracking systems.

Still referring to FIG. 23 , according to various embodiments, the CLCR1150 comprises one or more cholesteric liquid crystal (CLC) layers eachcomprising a plurality of chiral structures, wherein each chiralstructure comprises a plurality of liquid crystal molecules that extendin a layer depth direction (e.g., z-direction) and are successivelyrotated in a first rotation direction, as described supra. Thearrangements of the liquid crystal molecules of the chiral structuresvary periodically in a lateral direction perpendicular to the layerdepth direction such that the one or more CLC layers are configured tosubstantially Bragg-reflect a first incident light having a firstwavelength (λ₁) while substantially transmitting a second incident lighthaving a second wavelength (λ₂). As described above, each of the one ormore CLC layers are configured to substantially Bragg-reflectelliptically or circularly polarized first and second incident lighthaving a handedness of polarization that is matched to the firstrotation direction, when viewed in the layer depth direction, whilebeing configured to substantially transmit elliptically or circularlypolarized first and second incident light having a handedness ofpolarization that is opposite to the first rotation direction, whenviewed in the layer depth direction. According embodiments, thearrangements of the liquid crystal molecules varying periodically in thelateral direction are arranged to have a period in the lateral directionsuch that a ratio between the first wavelength and the period is betweenabout 0.5 and about 2.0. According to embodiments, the first wavelengthis in the near infrared range between about 600 nm and about 1.4 μm, forinstance about 850 nm and the second wavelength in is in the visiblerange having one or more colors as described elsewhere in thespecification. According to various embodiments, the liquid crystalmolecules of the chiral structures are pre-tilted relative to adirection normal to the layer depth direction. As configured, the one ormore CLC layers are configured such that the first incident light isreflected at an angle (OR) relative to the layer depth direction(z-direction) exceeding about 50°, about 60°, about 70° or about 80°degrees relative to the layer depth direction.

Thus configured, the wavelength-selective CLCR 1150 comprises one ormore cholesteric liquid crystal (CLC) layers each comprising a pluralityof liquid crystal molecules that extend in a layer depth direction andare successively rotated in a first rotation direction, whereinarrangements of the liquid crystal molecules of the chiral structuresvary periodically in a lateral direction perpendicular to the layerdepth direction such that the one or more CLC layers are configured tosubstantially Bragg-reflect a first incident light having a firstwavelength, e.g., an IR wavelength, while substantially transmitting asecond incident light having a second wavelength, e.g., a visiblewavelength.

Similar liquid crystal layers and structures may be used for thereflector 996 and coating 998 described above in connection with FIGS.17-20E. The coating 998 may for example comprise a liquid crystalcoating and may be wavelength and/or polarization selective in certainimplementations. Other types of coatings 998 and reflectors 996,however, may be employed.

As discussed above, for example, in connection with FIG. 16 , a lens 980may be used to alter the propagation of (e.g., collimate) light directedto the coupling optical element 944. This light may be light reflectedfrom, for example, the user's eye such as an anterior surface (e.g.,corneal surface) of the user's eye. The distance from the eye, e.g., theanterior surface (e.g., corneal surface) to the coupling optical element944 may be for example about 20 mm. A positive lens 980 such as a lenshaving a focal length of about 20 mm may be configured to collimatelight reflected from the eye 210, such as an anterior portion of the eye(e.g., the cornea). Light reflected form the anterior surface eye may becoupled into the waveguide 940 and guided therein to a camera. With thefocal length set at the distance to the anterior surface of the eye, thecamera can image such surfaces. Accordingly, in various implementationsthe positive lens 980 therefore may have a focal length that is equal orsubstantially equal to the distance of the lens to the portion of theeye 210 to be imaged, e.g., the cornea.

Although a refractive optical element is shown, other types of lenses oroptical elements with optical power such as positive optical power maybe used. For example, the lens may comprises a diffractive opticalelement such as a diffractive lens or hologram. Such a lens may bedisposed between the eye and the coupling optical element 944 in someimplementations.

In various implementations, the coupling optical element 944 may includeoptical power. The coupling optical element 944 may, for example,comprise a diffractive optical element having optical power. Thediffractive optical element may comprises, for example, a diffractivegrating. The diffractive optical element may comprise a holographicoptical element or a hologram. The diffractive optical element may havediffractive features such as for example surface features that areconfigured to both turn light into the waveguide and to provide opticalpower. Other types of diffractive optical elements are possible. Invarious implementations, the diffractive optical elements may compriseliquid crystal and may comprises liquid crystal gratings. Thediffractive optical elements may also comprise polarization grating.Additionally, the diffractive optical elements may comprise liquidcrystal polarization gratings. Some nonlimiting examples of liquidcrystal gratings, liquid crystal polarization gratings and other liquidcrystal optical elements are discussed in the following publishedapplications, each of which is hereby incorporated by reference hereinin its entirety and for all purposes: U.S. Publication No. 2018/0143438,titled “MULTILAYER LIQUID CRYSTAL DIFFRACTIVE GRATINGS FOR REDIRECTINGLIGHT OF WIDE INCIDENT ANGLE RANGES,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0143485, titled “SPATIALLY VARIABLE LIQUID CRYSTALDIFFRACTION GRATINGS,” filed on Nov. 16, 2017; U.S. Publication No.2018/0143509, titled “WAVEGUIDE LIGHT MULTIPLEXER USING CROSSEDGRATINGS,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017.

This diffractive optical element may have optical power that alters onthe propoagation of light incident thereon. The diffractive opticalelement, may for example, collimate light reflected from as surfacehaving a distance from said diffractive optical element corresponding tothe focal length of the diffractive optical element. Such distance maybe for example from about 15 to 20 mm (e.g., 20 mm or thereabouts). Sucha focal length may provide for collimating light reflected from ananterior surface of the eye such as a corneal surface (e.g., cornea).

FIG. 24 shows an example, of a coupling optical element (e.g., couplinggrating) 2111 disposed on a waveguide 2102 of an eyepiece 950. Thecoupling optical element 2111 comprises a diffractive optical elementconfigured to couple light incident thereon into the waveguide 2102. Thediffractive optical element also includes optical power. For example,the diffractive optical element includes diffractive features such assurface diffractive features that are configured to provide opticalpower, for example, to collimate light incident thereon from an anteriorsurface of the eye (e.g., corneal surface). A light consolidatingelement 2116, and an outcoupling optical element 2120 are also showndisposed on the waveguide 2102. The light consolidating element 2116 isdisposed to receive light coupled into the waveguide 2102 by thecoupling element 2111. The light consolidating element 2116 isconfigured to redirect light incident thereon from the coupling opticalelement 2111 to the out-coupling optical element 2120. The lightconsolidating element 2116 is configured to reduce lateral spatialextent of light (e.g., the light beam) from said at least one couplingelement prior to reaching said at least one out-coupling opticalelement, and an outcoupling optical element 2120. In certainconfigurations, fewer optical elements may be used, possibly, forexample, to reduce cost and/or optical losses or for other reasons. Forexample, the light consolidating element 2116 may be omitted in certainembodiments. In such embodiments, light may be incoupled from the inputcoupling element 2111 (e.g., after being reflected from the eye 210) anddirectly coupled to the outcoupling optical element 2120. The light maypropagate through the eyepiece 950 between the input coupling element2111 and the outcoupling optical element 2120. Other configurations arepossible. A camera is disposed with respect to the out-coupling opticalelement 2120 to receive light therefrom. The out-coupling opticalelement 2120 is configured to direct light received from the lightconsolidating element 2116 to the camera for capturing an image.

FIG. 24 also shows incoupling optical element 2104, a light distributingelement 2108, and an image content out-coupling optical element 2110disposed on the waveguide 2102. The incoupling optical element 2104 maybe configured to couple light received from an image projector into thewaveguide 2102. The light distribution element 2108 may be configured toredirect light received from the incoupling optical element 2104 to theout-coupling optical element 2110, additionally increasing the spatialextent of the light as discussed above. The out-coupling optical element2110 may be configured to couple light guided within the waveguide 2102out of the waveguide and direct such light to the eye for viewing imagecontent from the projector.

In various implementations one or more of these optical elements 2111,2116, 2120, 2110, 2108, 2104 may be disposed within or on a waveguide2102. Similarly, as discussed above, one or more of these opticalelements 2111, 2116, 2120, 2110, 2108, 2104 may comprise diffractiveoptical elements.

In the implementation illustrated in FIG. 24 , the coupling opticalelement (e.g., coupling grating) 2111 may be displaced lateral from theout-coupling optical element 2110 on the waveguide 2102. In theimplementation shown, a space laterally separates the coupling opticalelement 2111 from the out-coupling optical element 2110.

FIG. 25 shows another similar implementations wherein the couplingoptical element (e.g., coupling grating) 2111 is displaced lateral fromthe out-coupling optical element 2110 on the waveguide 2102. In theimplementation shown in FIG. 25 , however, a space does not laterallyseparate the coupling optical element 2111 from the out-coupling opticalelement 2110.

Having the coupling optical element (e.g., coupling grating) 2111 isdisplaced lateral from the out-coupling optical element 2110 on thewaveguide 2102 can enable the coupling optical element to includeoptical power, for example, that collimates light received from ananterior surface of the eye (e.g., corneal surface) such that thisoptical power does not affect the propagation of light from and/orthrough the out-coupling optical element 2110 to the eye. Imagespresented to the eye from the image projector as well as the view of theenvironment in front of the user and the head mounted display, need nottherefore be affected (e.g., distorted or defocused, etc.) by theoptical power of the coupling optical element 2111.

FIG. 26 illustrates an implementation of an imaging system 900configured to image multiple portions of the eye. For example, animaging system 900 such as shown in FIG. 26 may be configured to imageboth anterior surfaces of the eye (e.g., corneal surfaces) as well asthe retina. The imaging system 900 includes a pair of incoupling opticalelements, a first incoupling optical element 2111 a and a secondincoupling optical element disposed on the waveguide 2102 of theeyepiece. The imaging system 900 additionally includes a pair of lightconsolidating elements, a first light consolidating optical element 2116a and a second light consolidating element 2116 b disposed on thewaveguide 2102. In certain configurations, fewer optical elements may beused, possibly, for example, to reduce cost and/or optical losses or forother reasons. For example, the light consolidating elements 2116 a,2116 b may be omitted in certain embodiments. In such embodiments, lightmay be incoupled from the first and second input coupling elements 2111a, 2111 b (e.g., after being reflected from portions the eye 210 such asthe retina and/or cornea) and directly coupled to corresponding firstand second outcoupling optical elements 2120 a, 2120 b. The light maypropagate through the eyepiece 950 (e.g., via a waveguide such as thewaveguide 2102) between the first and second input coupling elements2111 a, 2111 b and the corresponding outcoupling optical elements 2120a, 2120 b. Other configurations are possible. In addition, the imagingsystem 900 additionally includes a pair of light out-couping opticalelements, a first out-coupling optical element 2120 a and a secondout-coupling optical element 2120 b disposed on the waveguide 2102.

The first coupling optical element 2111 a is configured to couple lightincident thereon into the waveguide 2102. The first light consolidatingelement 2116 a is disposed to receive light coupled into the waveguide2102 by the first coupling element 2111 a. The first light consolidatingelement 2116 a is configured to redirect light incident thereon from thefirst coupling optical element 2111 a to the first out-coupling opticalelement 2120 a. The first light consolidating element 2116 a is alsoconfigured to reduce the lateral spatial extent of light (e.g., thelight beam) from the first coupling element 2111 a prior to reaching thefirst out-coupling optical element 2120 a. A camera is disposed withrespect to the first out-coupling optical element 2120 a to receivelight therefrom. Although the camera is not shown in FIG. 26 , an areacorresponding to the detection area 2130 of the camera is shown. Thefirst out-coupling optical element 2120 a is configured to direct lightreceived from the first light consolidating element 2116 a to the cameraand, in particular, to the detection area 2130 shown in FIG. 26 forcapturing an image.

Likewise, the second coupling optical element 2111 b is configured tocouple light incident thereon into the waveguide 2102. The second lightconsolidating element 2116 b is disposed to receive light coupled intothe waveguide 2102 by the second coupling element 2111 b. The secondlight consolidating element 2116 b is configured to redirect lightincident thereon from the second coupling optical element 2111 b to thesecond out-coupling optical element 2120 b. The second lightconsolidating element 2116 b is also configured to reduce the lateralspatial extent of light (e.g., the light beam) from the second couplingelement 2111 a prior to reaching the second out-coupling optical element2120 a. A camera is disposed with respect to the second out-couplingoptical element 2120 b to receive light therefrom. Although the camerais not shown in FIG. 26 , an area corresponding to the detection area2130 of the camera is shown. The second out-coupling optical element2120 b is configured to direct light received from the second lightconsolidating element 2116 b to the camera and, in particular, to thedetection area 2130 shown in FIG. 26 for capturing an image.

FIG. 26 also shows incoupling optical element 2104, a light distributingelement 2108, and an image content out-coupling optical element 2110disposed on the waveguide 2102. The incoupling optical element 2104 maybe configured to couple light received from an image projector into thewaveguide 2102. The light distribution element 2108 may be configured toredirect light received from the incoupling optical element 2104 to theout-coupling optical element 2110, additionally increasing the spatialextent of the light as discussed above. The out-coupling optical element2110 may be configured to couple light guided within the waveguide 2102out of the waveguide and direct such light to the eye for viewing imagecontent from the projector.

In the implementation illustrated in FIG. 26 , the first and secondcoupling optical elements (e.g., coupling gratings) 2111 a, 2111 b aredisplaced lateral from the out-coupling optical element 2110 on thewaveguide 2102. In the implementation shown, a space laterally separatesthe first and second coupling optical elements 2111 a, 2111 b from theout-coupling optical element 2110. Furthermore, in the example of FIG.26 , the first and second coupling optical elements 2111 a, 2111 b aredisplaced lateral from each other on the waveguide 2102. In otherimplementations, two or more of the first coupling optical element(e.g., coupling grating) 2111 a, the second coupling optical element2111 b, and the out-coupling optical element 2110 need not be displacedlaterally from each other on the waveguide 2102.

In various implementations one or more of these optical elements 2111 a,2111 b, 2116 a, 2116 b, 2120 a, 2120 b, 2110, 2108, 2104 may be disposedwithin or on a waveguide 2102. Similarly, as discussed above, one ormore of these optical elements 2111 a, 2111 b, 2116 a, 2116 b, 2120 a,2120 b, 2110, 2108, 2104 may comprise diffractive optical elements.

The imaging system 900 of FIG. 26 can be configured to image multipleportions of the eye. For example, an imaging system 900 may beconfigured to image both anterior surfaces of the eye (e.g., cornealsurfaces) as well as the retina. The first incoupling optical element2111 a, may for example have optical power or have a lens disposed infront thereof with optical power. The first coupling optical element2111 a, may for example comprise a diffractive optical elementconfigured to couple light into the waveguide 2102 but also configuredto impart optical power thereto. Additionally or alternatively, a lenshaving optical power may be disposed in front of the first couplingoptical element 2111 a. The optical power may be configured to alter thepropagation of light received by the first incoupling optical element2111 a such that a particular portion of the eye may be image. In someexamples, the optical power may be positive optical power. Moreover, theoptical power may be such that an anterior surface of the eye may beimaged. The optical power may, for example, correspond to a focal lengthof between about 15 to 25 mm (e.g., about 20 mm). As a result, lightreflected from an anterior surface of the eye, which may be about 15 to25 mm (e.g., about 20 mm) from the first coupling optical element 2111 amay be collimated and coupled into the waveguide.

In contrast, in various implementations, the second coupling opticalelement 2111 b may neither have optical power nor include a lensdisposed in front thereof. The lack of optical power associated with thesecond coupling optical element 2111 b will result in light from theanterior portion of the eye (e.g., corneal surfaces) not beingcollimated and not being imaged by the camera. However, light reflectedfrom the retina may upon passing through the natural lens of the eye ofthe user be collimated. This light collimated by the natural lens of theeye may be coupled into the waveguide 2102 by the second couplingoptical element 2111 b and imaged by the camera. In this manner, lightcollected by the first coupling optical element 2111 a may image ananterior surface of the eye (e.g., a corneal surface of the eye) and thesecond coupling optical element 2111 b may image the retina of the eyeof the user. In some implementations, such a configuration enables lightcollected by the first coupling optical element 2111 a to form images ofglint on the eye, for example, on image an anterior surface of the eye(e.g., a corneal surface of the eye). The second coupling opticalelement 2111 b may image the retina of the eye of the user as discussedabove. In some examples, the second coupling optical element 2111 band/or a lens disposed in front thereof may have some amount of netoptical power (e.g., a non-zero amount of net optical power) that isweaker than that of the first coupling optical element 2111 a and/or alens disposed in front of the first coupling optical element 2111 a.

In some implementations, the images formed by light collected by thefirst coupling optical element 2111 a are next to (e.g., notsuperimposed over) images formed by light collected by the secondcoupling optical element 2111 b. For example, images of the anteriorsurface(s) of the user's eye (e.g., cornea) may be formed next to (e.g.,not superimposed over) images of the retina.

Polarization techniques can be used to attenuate or remove light fromthe anterior surfaces (e.g., corneal surfaces) from affecting imagesformed by light collected by the second coupling optical element 2111 b.For example, the eye can be illuminated with polarized light having afirst polarization and the camera can form an image using light fromsecond out-coupling optical element 2120 b using light of a seconddifferent polarization. For example, the second out-coupling opticalelement 2111 b may be a polarization selective coupling element thatselectively couple out light of the second polarization different thanthe first polarization. Additionally or alternatively, a polarizer 2140that filters out the first polarization (e.g., selectively transmits thesecond polarization) may be included between the second out-couplingoptical element 2120 b and the camera 920 as illustrated in FIG. 27 ,which is a cross-section through the waveguide 950, 2102, consolidatingoptical elements 2116 a, 2116 b, and out-coupling optical elements 2120a, 2120 b shown in FIG. 26 .

Such a configuration may be used to reduce unwanted reflections (e.g.,glint), such as from the cornea when imaging the retina. Reflection fromthe cornea will be specular. Accordingly, if light of the firstpolarization is incident on the cornea, the light reflected from thecornea will retain that first polarization. In contrast, the retina isdiffuse. If light of the first polarization is incident on the retina,the light reflected from the retina does not retain solely the firstpolarization. The diffuse reflection more likely results in unpolarizedlight. Accordingly, the second polarization, different from the firstpolarization will be present in the light reflected from the retina. Asa result, by forming images with light coupled out of the secondout-coupling optical element 2120 b using light of the secondpolarization, images of the retina will be obtained while images of thecornea or glint will be suppressed. Likewise, by illuminating with afirst polarization and imaging with a second different polarization, theretina can be image with reduced glare from the cornea.

Accordingly, in various implementations, polarization specific opticalfilters or polarization selective optical element (e.g. couplinggratings) may be used to reduce unwanted reflected light from the eye210 (e.g., from the cornea). For example, unwanted light, glare, orglint may be reflected off the cornea that may saturate an imagecaptured by the camera. As discussed above, light reflected from thecornea may be specular and maintain its polarization. By contrast, lightreflected off the retina may be more diffusely reflected and may be lesshomogenously polarized. Likewise, a combination of polarizers may beused to remove some or most of the unwanted light reflected from thecornea. Initially polarized light can be used for illuminating the eyeof the user. In some designs, a polarized illumination source (e.g., thelight source) may be used. Additionally or alternatively, a firstpolarizer (e.g., a polarization specific optical filter or apolarization selective optical coupling element coupling illuminationlight into an illumination waveguide) may be positioned at the beginningof the optical path of the illumination source to provide initialpolarization of the light to the eye. A second polarizer (e.g., apolarization specific optical filter or polarization selective couplingelement) may be positioned at the optical path before the light entersthe camera. The second polarizer may be rotated at 90° from the firstpolarizer (e.g. the polarizers may be “crossed”). As a result, the eyewill be illuminated with the first polarization with some light of thefirst polarization reflected from the cornea. This light will not passthrough the crossed polarizer (that preferentially passes light of thesecond polarization) located proximal the camera. However, lightreflected from the retina will include the second polarization.Likewise, light diffusely reflected from the retina will pass throughthe polarizer 2140 proximal the camera and will enable an image of theretina to be captured by the camera. Thus, in such configurations,unwanted light received from the eye (e.g., from cornea) and enteringthe camera may be reduced or eliminated from the image captures usinglight from the second coupling optical element 2111 b. Otherconfigurations are possible. For example, a polarization selectivecoupling elements 2111 b and/or a polarization selective out-couplingoptical elements 2120 b may be used in addition or in alternative topolarizers such as the polarizer 2140 proximal the camera. The effectmay again be to reduce or remove unwanted light received from the eye(e.g., from cornea) before entering the imaging device 920.

As illustrated in FIG. 27 , in various implementations, such polarizersare not used in an optical path from the first coupling optical element2111 a and the camera or between the first out-coupling optical element2120 a and the camera. As a result, images of the cornea and glint maybe obtained from light coupled by the first coupling optical element2111 a into the waveguide and/or light coupled out of the waveguide fromthe first out-coupling optical element 2120 a. As discussed above, thisfirst coupling optical element 2111 a may have optical power or a lensassociated therewith that is specifically used to image the corneaand/or glint. Likewise, polarization selective coupling optical elements2111 a or polarization selective out-coupling optical element 2120 athat filter out light of the first polarization would not be used as thefirst coupling optical element 2111 a and out-coupling optical element2120 a, respectively. Additionally, polarizers 2140 between the couplingoptical element 2111 a and the camera 920 or between the out-couplingoptical element 2111 a and the camera 920 that filter out light of thefirst polarization would not be used.

A wide variety of variations are possible. For example, although thefirst and second out-coupling optical elements 2120 a, 2120 b aredescribed above as coupling light and forming images on a single camera(e.g., a single detection area 2130), in other implementations, thefirst and second out-coupling optical elements 2120 a, 2120 b cancoupling light and forming images on respective first and secondcameras. Other variations are possible.

In some implementations, one or more of the eyepieces described above(e.g., the eyepiece 950) with reference to FIGS. 24-27 may be dedicatedimaging eyepiece layer (e.g., omitting the incoupling optical element2104, the light distributing element 2108, and/or the output couplingelement 2110). In such implementations, the imaging eyepiece layer maybe included as a layer in a stack of waveguides. The one or more otherlayers in the stack of waveguides may include the incoupling opticalelement 2104, the light distributing element 2108, and/or the outputcoupling element 2110.

In some embodiments, the dedicated imaging eyepiece layer can beconfigured to capture images of the environment. In some suchembodiments, the imaging eyepiece layer may be disposed most proximal tothe environment when installed in the head-mounted display. In some suchconfigurations, the dedicated imaging eyepiece layer may be theoutermost layer in the waveguide stack such that it is positionedbetween the other layers (e.g., waveguides) and the environment. In someembodiments, the dedicated imaging eyepiece layer can be configured tocapture images of the user's eye 210. In some such embodiments, theimaging eyepiece layer may be disposed most proximal to the user wheninstalled in the head-mounted display. In some implementations, thededicated imaging eyepiece layer may be the innermost layer in thewaveguide stack such that it is positioned between the other layers(e.g., waveguides) and the user. Other configurations are possible.

In certain embodiments, the first and second coupling elements 2111 a,2111 b may be laterally aligned but displaced in depth (e.g., along thez-axis or into the page of FIG. 26 ). For example, in such embodiments,the first and second coupling elements 2111 a, 2111 b may be positionedon opposite sides of the same waveguide. In certain embodiments, thefirst input coupling element 2111 a may be disposed on or within a firstwaveguide and the second input coupling element 2111 b. Additionally oralternatively, the first and second light consolidating elements 2116 a,2116 b and/or the first and second outcoupling optical elements 2120 a,2120 b may be disposed on opposite sides of the same waveguide and/ormay be disposed on or in corresponding separate waveguides.

One or more of the coupling optical elements 2111, 2111 a, 2111 bdescribed above with reference to FIGS. 24-27 may bewavelength-selective such that the optical elements are configured tointeract only with a certain wavelength or band of wavelengths. Thewavelength or band of wavelengths may include invisible light (e.g.,infrared light, or a specific band thereof). In some implementations,the first input coupling element 2111 a may be configured to operate ona wavelength lower than that for the second input coupling element 2111b (or vice versa). For example, the first coupling optical element 2111a may be configured to interact with about 800 nm light, and/or thesecond coupling optical element 2111 b may be configured to interactwith about 950 nm light (or vice versa). Optical filters may also beused to effectuate similar wavelength selection. In variousimplementations, therefore, light coupled into the waveguide by thefirst coupling optical element that reaches the at least one can be of adifferent wavelength than light coupled into the waveguide by the secondoptical element that reaches the at least one camera. Otherconfigurations are possible.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense.

Indeed, it will be appreciated that the systems and methods of thedisclosure each have several innovative aspects, no single one of whichis solely responsible or required for the desirable attributes disclosedherein. The various features and processes described above may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure.

Certain features that are described in this specification in the contextof separate embodiments also may be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment also may be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially exampled as such, one or more featuresfrom an exampled combination may in some cases be excised from thecombination, and the exampled combination may be directed to asubcombination or variation of a subcombination. No single feature orgroup of features is necessary or indispensable to each and everyembodiment.

It will be appreciated that conditional language used herein, such as,among others, “can,” “could,” “might,” “may,” “e.g.,” and the like,unless specifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/or stepsare included or are to be performed in any particular embodiment. Theterms “comprising,” “including,” “having,” and the like are synonymousand are used inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list. Inaddition, the articles “a,” “an,” and “the” as used in this applicationand the appended examples are to be construed to mean “one or more” or“at least one” unless specified otherwise. Similarly, while operationsmay be depicted in the drawings in a particular order, it is to berecognized that such operations need not be performed in the particularorder shown or in sequential order, or that all illustrated operationsbe performed, to achieve desirable results. Further, the drawings mayschematically depict one more example processes in the form of aflowchart. However, other operations that are not depicted may beincorporated in the example methods and processes that are schematicallyillustrated. For example, one or more additional operations may beperformed before, after, simultaneously, or between any of theillustrated operations. Additionally, the operations may be rearrangedor reordered in other embodiments. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the embodiments describedabove should not be understood as requiring such separation in allembodiments, and it should be understood that the described programcomponents and systems may generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other embodiments are within the scope of the followingexamples. In some cases, the actions recited in the examples may beperformed in a different order and still achieve desirable results.

Accordingly, the disclosure are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein. A variety of example systems and methods are providedbelow.

EXAMPLES Example Section I

1. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user, said head-mounted display system comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project images into the user's        eye to display image content in the vision field of the user;    -   a camera;    -   at least one waveguide;    -   at least one coupling optical element configured such that light        is coupled into said waveguide and guided therein; and    -   at least one out-coupling element configured to couple light        guided within said waveguide out of said waveguide and direct        said light to said camera,    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light that is coupled into said waveguide        via the coupling element and guided therein and that is coupled        out from said waveguide by said outcoupling coupling element        such that images may be captured by said camera.

2. The system of Example 1, wherein said at least one coupling opticalelement is configured such that light from the environment in front ofthe user wearing the head mounted display system is coupled into said atleast one waveguide and guided therein such that images of saidenvironment may be captured by said camera.

3. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said at least one waveguide and guided therein such that images ofsaid eye may be captured by said camera.

4. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said waveguide and guided therein such that images of said eye maybe captured by said camera, said system configured to image an anteriorportion of said eye.

5. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said waveguide and guided therein such that images of said eye maybe captured by said camera, said system configured to image a cornealsurface of said eye.

6. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said waveguide and guided therein such that images of said eye maybe captured by said camera, said system configured to image the retinaof said user's eye.

7. The system of any of the Examples above, further comprising aneyepiece disposed on the frame, said eyepiece configured to direct lightinto said user's eye to display augmented reality image content to theuser's vision field, at least a portion of said eyepiece beingtransparent and disposed at a location in front of the user's eye whenthe user wears said head-mounted display such that said transparentportion transmits light from an environment in front of the user to theuser's eye to provide a view of the environment in front of the user.

8. The system of Example 7, wherein said eyepiece is configured toreceive light from said image projector and to direct said light intosaid user's eye to display augmented reality image content to the user'svision field.

9. The system of any of Examples 7-8, wherein said eyepiece comprisessaid at least one waveguide.

10. The system of any of Examples 7-9, wherein said image projector isconfigured to direct light into an edge of said eyepiece.

11. The system of Examples 9 or 10, wherein said image projector isconfigured to direct light into an edge of said at least one waveguide.

12. The system of any of the Examples above, further comprising at leastone in-coupling optical element configured to in-couple light from saidimage projector into said at least one waveguide so as to guide lightfrom said image projector for providing said image content to saiduser's eye.

13. The system of any of the Examples above, wherein said at least onecoupling optical element is also configured to couple light from saidimage projector guided within said waveguide out of said at least onewaveguide such that image content can be viewed by the user's eye.

14. The system of any of the Examples above, wherein the same couplingoptical element is configured to couple light from said image projectorguided within said waveguide out of said waveguide such that imagecontent can be viewed by the user's eye and to couple light into said atleast one waveguide to be guided therein to said camera.

15. The system of any of Examples 1 to 12, further comprising at leastone image content out-coupling optical element configured to couplelight from said image projector guided within said waveguide out of saidat least one waveguide such that image content can be viewed by theuser's eye.

16. The system of any of the Examples above, wherein said at least onecoupling optical element faces the eye of the user wearing the headmounted imaging system to receive light from said eye.

17. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light from theenvironment in front of the user wearing the head mounted imaging systemis coupled into said at least one waveguide and guided therein such thatimages of said environment may be captured by said camera.

18. The system of any of the Examples above, wherein said at least onecoupling optical element faces the environment in front of the userwearing the head mounted imaging system to receive light from saidenvironment.

19. The system of Example 15, wherein said at least one image contentout-coupling optical element configured to couple light from said imageprojector guided within said waveguide out of said at least onewaveguide and said at least one coupling optical element configured suchthat light is coupled into said waveguide and guided therein to saidcamera are superimposed on each other.

20. The system of Example 15, wherein said at least one image contentout-coupling optical element configured to couple light from said imageprojector guided within said waveguide out of said at least onewaveguide and said at least one coupling optical element configured suchthat light is coupled into said waveguide and guided therein to saidcamera are stacked over the other.

21. The system of Example 15, wherein said at least one image contentout-coupling optical element configured to couple light from said imageprojector guided within said waveguide out of said at least onewaveguide and said at least one coupling optical element configured suchthat light is coupled into said waveguide and guided therein to saidcamera are integrated in the same diffractive optical element.

22. The system of Example 15, wherein said at least one coupling opticalelement is configured such that light is coupled into a first waveguideand guided therein to said camera and said at least one image contentout-coupling optical element is configured to couple light from saidimage projector guided within a second waveguide out of said secondwaveguide.

23. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light is coupled into afirst waveguide and guided therein to said camera and said imageprojector is configured to couple light into a second waveguide toprovide image content to said eye.

24. The system of any of the Examples above, wherein said imageprojector comprises a light source, a modulator, and projection optics.

25. The system of any of the Examples above, wherein the image projectorcomprises scanning optical fiber.

26. The system of any of Examples 24 or 25, wherein the modulatorcomprises a light modulator.

27. The system of Example 26, wherein the light modulator comprises aspatial light modulator.

28. The system of any of the Examples above, wherein said cameracomprises a detector array and imaging optics.

29. The system of Example 28, wherein said imaging optics is configuredto focus collimated light onto said detector array.

30. The system of any of the Examples above, wherein said at least onewaveguide comprises material that is transparent to visible light havinga refractive index sufficient to guide light in said waveguide by totalinternal reflection.

31. The system of any of the Examples above, wherein said at least onewaveguide comprises a stack of waveguides.

32. The system of Example 31, wherein different waveguides of the stackof waveguides are configured to output light with different wavefrontdivergence as if projected from different distances from the user's eye.

33. The system of Example 31 or 32, wherein different waveguides of thestack of waveguides are configured to output light with differentcolors.

34. The system of any of Examples 31, 32, or 33, wherein differentwaveguides comprise first, second, and third waveguides, said system isconfigured such that the first is for red color light, the second for isgreen color light, and the third is for blue color light.

35. The system of any of the Examples 12 to 34, wherein the in-couplingoptical element comprises a diffractive optical element or reflector.

36. The system of any of the Examples 12 to 34, wherein the in-couplingoptical element comprises a diffractive optical element.

37. The system of any of the Examples above, wherein the couplingoptical element comprises a diffractive optical element.

38. The system of any of the Examples above, wherein the couplingoptical element comprises liquid crystal.

39. The system of any of the Examples above, wherein the couplingoptical element comprises a liquid crystal polarization grating.

40. The system of any of the Examples above, wherein the out-couplingoptical element comprises a diffractive optical element.

41. The system of any of the Examples above, wherein the couplingoptical element comprises liquid crystal.

42. The system of any of the Examples above, wherein the couplingoptical element comprises a liquid crystal polarization grating.

43. The system of any of the Examples above, wherein the couplingelement is configured to increase a dimension of the eyebox along atleast one axis.

44. The system of Example 43, further comprising an orthogonal pupilexpander comprising at least one light redirecting element in or on saidat least one waveguide that is configured to increase a dimension of aneyebox along an axis that is orthogonal to the at least one axis.

45. The system of Example 44, wherein said at least one lightredirecting element comprises a diffractive optical element.

46. The system of any of the Examples above, wherein the same couplingelement is configured to (a) couple light into said at least onewaveguide to be received by said camera and to (b) couple light fromsaid image projector out from said at least one waveguide to said user'seye.

47. The system of any of the Examples above, wherein the same couplingelement is configured to (a) couple light from said environment intosaid at least one waveguide to be received by said camera and to (b)couple light from said image projector out from said at least onewaveguide to said user's eye.

48. The system of any of the Examples above, wherein the same couplingelement is configured to (a) couple light from said eye into said atleast one waveguide to be received by said camera and to (b) couplelight from said image projector out from said at least one waveguide tosaid user's eye.

49. The system of any of the above Examples, further comprising areflective surface having optical power disposed to receive lightreflected from the user's eye that passes through said eyepiece and todirect said light back to said eyepiece.

50. The system of Example 49, wherein said at least one coupling elementis configured such that light from the user's eye that passes throughthe at least one waveguide and is reflected from the reflective surfaceback to the at least one waveguide is coupled into said at least onewaveguide and guided therein.

51. The system of any of Examples 49 to 50, wherein the camera isdisposed in an optical path with respect to said at least oneout-coupling optical element to receive at least a portion of the lightfrom the user's eye that is reflected from the reflective surface andcoupled into said waveguide via the coupling element and guided thereinand that is coupled out from said waveguide by said outcoupling couplingelement.

52. The system of any of Examples 49 to 51, wherein the reflectivesurface reflects infrared light but transmits visible light.

53. The system of any of Examples 49 to 52, wherein the reflectivesurface is curved.

54. The system of any of Examples 49 to 53, wherein the reflectivesurface is disposed on a curved optical element.

55. The system of any of Examples 49 to 54, wherein the reflectivesurface is disposed on a concave mirror.

56. The system of any of Examples 49 to 55, wherein the reflectivesurface has positive optical power in reflection and negligible opticalpower in transmission.

57. The system any of Examples 49 to 56, wherein the reflective surfaceis configured to collimated light from the user's eye.

58. The system of any of Examples 49 to 57, wherein the reflectivesurface is configured to collimate light from the retina of the user'seye.

59. The system of any of Examples 49 to 58, wherein the reflectivesurface is configured to collimate light from an anterior region of theuser's eye.

60. The system of any of Examples 49 to 59, wherein the reflectivesurface is configured to collimate light from the cornea of the user'seye.

61. The system of any of Examples 49 to 60, wherein the reflectivesurface is formed on a curved optical element and comprises an infraredreflective coating.

62. The system of Example 61, wherein the curved optical element hasnegligible power for light transmitted therethrough.

63. The system of Example 61 or 62, wherein the curved optical elementhas first and second curved surfaces on opposite sides of the curvedoptical element, said first and second curved surfaces having the samecurvature.

64. The system of any of Examples 49 to 63, further comprising aretarder disposed with respect to the reflective surface and thecoupling optical element so as to rotate the polarization of lightpassing through the at least one waveguide and reflected from thereflective surface back to the at least one waveguide and the couplingoptical element.

65. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization selective turning element.

66. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization grating.

67. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn light guided within the at leastone waveguide out of the waveguide to the eye as collimated lightdirected to the eye of the user.

68. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn collimated light from thereflective surface into the at least one waveguide.

69. The system of any of the Examples above, wherein the at least oneout-coupling element comprises an off-axis reflector.

70. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization selective turning element.

71. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization grating.

72. The system of any of the Examples above, wherein the at least oneout-coupling element comprises liquid crystal.

73. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a liquid crystal polarization grating.

74. The system of any of the Examples above, further comprising acircular polarizer.

75. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization selective turning element.

76. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization grating.

77. The system of any of the Examples above, wherein the at least onein-coupling element comprises a diffractive optical element.

78. The system of any of the Examples above, wherein the at least onein-coupling element comprises a diffraction grating.

79. The system of any of the Examples above, wherein the in-couplingelement comprises an off-axis reflector.

80. The system of any of Examples 49 to 79, wherein the reflectivesurface comprises a liquid crystal reflector.

81. The system of any of Examples 49 to 80, wherein the reflectivesurface comprises a cholesteric liquid crystal reflective lens.

82. The system of any of the Examples above, wherein the same waveguide(a) guides light coupled from the user's eye into said at least onewaveguide to be received by said camera so as to capture an image of atleast a portion of the eye of the user, and (b) guides light coupledfrom said image projector such that light from said projector can bedirected to said user's eye such that said image from said imageprojector is in the vision field of said the user.

83. The system of any of the Examples above, wherein the same couplingelement (a) couples light from said user's eye into said at least onewaveguide to be received by said camera and (b) couples light from saidimage projector out from said at least one waveguide to said user's eye.

84. The system of any of Examples 49 to 83, further comprisingelectronics configured to cause the camera to capture a first image whenlight reflected from the reflective surface is blocked.

85. The system of Example 84, wherein said electronics is configured tocause the camera to capture a second image when light reflected from thereflective surface is not blocked.

86. The system of Example 85, wherein said electronics is configured touse the first image to modify the second image.

87. The system of Examples 85 or 86, wherein said electronics isconfigured to subtract from the second image based on the first image.

88. The system of any of the Examples above, wherein said system isconfigured to perform eye tracking based images of said eye.

89. The system of Example 88, wherein performing eye tracking based onsaid images of said eye comprises storing an image of the retina of saideye.

90. The system of any of any of the Examples above, wherein said systemis configured to:

-   -   obtain an image of a portion of said retina of said eye using        said camera;    -   compare one or more stored images of said retina with the image        of said portion of said retina; and    -   determine a gaze of the user based on the comparison of the one        or more stored images and the image of the portion of the retina        obtained from the camera.

91. The system of Example 90, wherein determining a gaze of the usercomprises determining to which portion of the retina corresponds to theimage of said portion of the retina.

92. The system of any of Examples 90 to 91, wherein determining a gazeof the user comprises determining an orientation of the eye.

93. The system of any of the Examples above, wherein said system isconfigured to obtain biometric data based on one or more images of theuser's eye obtained with said camera.

94. The system of any of the Examples above, wherein said system isconfigured to identify the user via biometric sensing based on one ormore images of said eye obtained with said camera.

95. The system of any of the above Examples, wherein said system isconfigured to provide illumination of a first polarization and topreferentially capture images with said camera using light of a secondpolarization different than said first polarization.

96. The system of any of the above Examples, wherein said system isconfigured to illuminate said user's eye with light of a firstpolarization and to preferentially capture images of said user's eyewith said camera using light of a second polarization different thansaid first polarization.

97. The system of Examples 95 or 96, wherein said first and secondpolarizations are orthogonal.

98. The system of any of the above Examples, further comprising a lightsource disposed so as to provide illumination so as to capture imageswith said camera.

99. The system of any of the above Examples, further comprising a lightsource disposed so as to illuminate of the user's eye.

100. The system of Examples 98 or 99, wherein said light sourcecomprises one or more infrared light sources.

101. The system of any of Examples 98 to 100, wherein said light sourcecomprises one or more infrared light emitting diodes (LEDs).

102. The system of any of Examples 98 to 101, wherein said light sourceis pulsed.

103. The system of any of Examples 98 to 102 further comprising anoff-axis reflector disposed to receive light from said light source andilluminate said user's eye with said light.

104. The system of any of Examples 98 to 103, wherein said light sourceis configured to input light into a waveguide to provide saidillumination.

105. The system of any of Examples 98 to 104, wherein said light sourceis configured to input light into a waveguide disposed with respect tosaid eye to provide illumination to said eye.

106. The system of Examples 104 or 105, further comprising anillumination in-coupling optical element configured to couple light fromsaid light source into said waveguide.

107. The system of any of Examples 98 to 103, wherein said light sourceis configured to input light into said at least one waveguide to provideillumination.

108. The system of Example 107, further comprising an illuminationin-coupling optical element configured to couple light from said lightsource into said at least one waveguide to provide illumination.

109. The system of any of Examples 98 to 103, wherein said light sourceis configured to input light into the same waveguide as used to projectimage content to the user's eye.

110. The system of any of Examples 98 to 104, wherein said light sourceis configured, to provide illumination to the user's eye, to input lightinto the same waveguide as used to guide light to the camera.

111. The system of any of Examples 98 to 105, wherein said light sourceis configured to input light into the same waveguide as used to guidelight from the user's eye to the camera.

112. The system of ant of Examples 109 to 111, further comprising anillumination in-coupling optical element configured to couple light fromsaid light source into said waveguide.

113. The system of any of Examples 106, 108, or 112, wherein saidillumination in-coupling optical element is polarization selective,in-coupling light of a first polarization.

114. The system of Example 98 to 113, wherein said light source is apolarized light source configured to output polarized light having afirst polarization.

115. The system of any of Examples 98 to 114, wherein said light sourceis configured to direct polarized light having a first polarization ontosaid eye.

116. The system of Example 98 to 115, further comprising an illuminationpolarizer having a first polarization disposed in the optical pathbetween said light source and said eye to polarize light directed tosaid eye.

117. The system of Example 116, wherein the illumination polarizer isdisposed in the optical path between said light source and saidwaveguide configured to provide illumination.

118. The system of any of Examples 98 to 117, further comprising animage acquisition polarizer in an optical path between said eye and saidcamera.

119. The system of Example 118, wherein said image acquisition polarizeris proximal said camera.

120. The system of Examples 118 or 119, wherein said image acquisitionpolarizer is disposed in an optical path between (a) said at least onewaveguide configured guide light to said camera and (b) said camera.

121. The system of any of Examples 118 to 120, wherein said imageacquisition polarizer reduces the amount of light said firstpolarization that reaches said camera.

122. The system of Examples 118 to 121, wherein said image acquisitionpolarizer comprises a polarizer configured to selectively coupling lightof a second polarization different than said first polarization to saidcamera.

123. The system of any of the Examples above, further comprising atleast one light consolidating element disposed in an optical pathbetween said at least one coupling element and said at least oneout-coupling optical element to reduce lateral spatial extent of lightfrom said at least one coupling element prior to reaching said at leastone out-coupling optical element.

124. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a diffractive optical element.

125. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a hologram or diffraction grating.

126. The system of any of the Examples above, wherein said at least onewaveguide comprises material that is transparent to infrared lighthaving a refractive index sufficient to guide infrared light in saidwaveguide by total internal reflection.

127. The system of any of the Examples above, wherein said at least onecoupling optical element comprises an exit pupil expander.

128. The system of any of the Examples above, wherein the systemincludes optical power to increase collimation of light reflected fromthe eye that is coupled into the waveguide to be guided to the camera.

129. The system of any of the Examples above, wherein the systemincludes optical power to increase collimation of light reflected froman anterior portion of the eye that is coupled into the waveguide to beguided to the camera.

130. The system of any of the Examples above, wherein the systemincludes optical power to increase collimation of light reflected fromthe cornea of the eye that is coupled into the waveguide to be guided tothe camera.

131. The system of any of Examples 128 to 130, wherein the optical powercomprises positive optical power.

132. The system of any of Examples 128 to 131, wherein the optical poweris provided by a lens.

133. The system of any of Examples 88 to 132, wherein the one or morestored images of the retina of the eye comprise a composite image of theretina of the eye generated using a plurality of images of differentportions of the retina of the eye.

134. The system of any of Examples 88 to 133, wherein the compositeimage of the retina comprises a plurality of images of the retinastitched together.

135. The system of any of Examples 88 to 134, wherein the plurality ofimages of the retina stitched together comprises images obtained when afixation target was displayed in the vision field of the user at variouslocations, respectively.

136. The system of any of Examples 88 to 135, wherein the one or morestored images of the retina comprises images obtained when a fixationtarget was displayed in the vision field of the user at variouslocations, respectively.

137. The system of any of Examples 88 to 136, wherein the system isfurther configured to use the obtained image of the portion of theretina of the eye to update the composite image.

138. The system of any of Examples 88 to 137, wherein using the obtainedimage of the portion of the retina to update the composite image of theretina comprises stitching the obtained image into a section of thecomposite image corresponding to the portion of the retina shown in theobtained image.

139. The system of any of Examples 88 to 138, wherein the system isfurther configured to apply a digital filter to the obtained image ofthe portion of the retina of the eye to obtain a filtered image of theportion of the retina.

140. The system of Examples 139, wherein the system is furtherconfigured to compare one or more stored images of the retina with thefiltered image of the portion of the retina.

141. The system of any of Examples 139 to 140, wherein the digitalfilter comprises a Frangi Filter.

142. The system of any of Examples 88 to 139, wherein the system isconfigured to apply edge enhance the obtained image of the portion ofthe retina.

143. The system of any of the Examples above, wherein said system isconfigured to perform user identification verification using images ofthe retina.

144. The system of any of the Examples above, wherein said system isconfigured to:

-   -   obtain an image of a portion of said retina of said eye using        said camera;    -   compare one or more stored images of said retina with the image        of said portion of said retina.

145. The system of Example 144, wherein the one or more stored images ofthe retina of the eye comprise a composite image of the retina of theeye generated using a plurality of images of different portions of theretina of the eye.

146. The system of any of Examples 144 to 145, wherein the compositeimage of the retina comprises a plurality of images of the retinastitched together.

147. The system of any of Examples 144 to 146, wherein the plurality ofimages of the retina stitched together comprises images obtained when afixation target was displayed in the vision field of the user at variouslocations, respectively.

148. The system of any of Examples 144 to 146, wherein the one or morestored images of the retina comprises images obtained when a fixationtarget was displayed in the vision field of the user at variouslocations, respectively.

149. The system of any of Examples 144 to 148, wherein the system isfurther configured to use the obtained image of the portion of theretina of the eye to update the composite image.

150. The system of any of Examples 144 to 149, wherein using theobtained image of the portion of the retina to update the compositeimage of the retina comprises stitching the obtained image into asection of the composite image corresponding to the portion of theretina shown in the obtained image.

151. The system of any of Examples 144 to 150, wherein the system isfurther configured to apply a digital filter to the obtained image ofthe portion of the retina of the eye to obtain a filtered image of theportion of the retina.

152. The system of Examples 151, wherein the system is furtherconfigured to compare one or more stored images of the retina with thefiltered image of the portion of the retina.

153. The system of any of Examples 144 to 152, wherein the digitalfilter comprises a Frangi Filter.

154. The system of any of Examples 144 to 153, wherein the system isconfigured to apply edge enhance the obtained image of the portion ofthe retina.

Example Section II

1. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user and to image at least a portion of an environment in frontof the user wearing the head mounted display system, said head-mounteddisplay system comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project an image;    -   a camera; and    -   an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        the environment in front of the user to the user's eye to        provide a view of the environment in front of the user, said        eyepiece comprising:        -   (a) at least one waveguide;        -   (b) at least one in-coupling optical element configured to            in-couple light from said image projector into said at least            one waveguide so as to guide light from said image projector            therein;        -   (c) at least one coupling optical element configured to            couple light from said image projector guided within said            waveguide out of said waveguide and direct said light to the            user's eye; and        -   (d) at least one out-coupling element configured to couple            light within said waveguide out of said waveguide and direct            said light to said camera,    -   wherein the image projector is disposed in an optical path with        respect to said at least one in-coupling optical element to        couple light from said image projector into said waveguide to be        guided therein such that said light is coupled out from said        waveguide by said at least one coupling element to said user's        eye such that said image from said projector is in the vision        field of said the user,    -   wherein said coupling element is configured such that light from        the environment in front of the user wearing the head mounted        display is coupled into said waveguide and guided therein,    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light from the environment in front of        the user that is coupled into said waveguide via the coupling        element and guided therein and that is coupled out from said        waveguide by said outcoupling coupling element such that images        of said environment may be captured by said camera, and    -   wherein the same waveguide (a) guides light coupled from said        environment into said waveguide to be received by said camera so        as to capture an image of at least a portion of the environment        in front of the user, and (b) guides light coupled from said        projector such that light from said projector can be directed to        said user's eye so that said image from said projector is in the        vision field of said the user.

2. The system of Example 1, wherein said image projector comprises alight source, a modulator, and projection optics.

3. The system of Example 1 or 2, wherein the image projector comprisesscanning optical fiber.

4. The system of any of Examples 2 or 3, wherein the modulator comprisesa light modulator.

5. The system of Example 4, wherein the light modulator comprises aspatial light modulator.

6. The system of any of the Examples above, wherein said cameracomprises a detector array and imaging optics.

7. The system of Example 6, wherein said imaging optics is configured tofocus collimated light onto said detector array.

8. The system of any of the Examples above, wherein said at least onewaveguide comprises material that is transparent to visible light havinga refractive index sufficient to guide light in said waveguide by totalinternal reflection.

9. The system of any of the Examples above, wherein said at least onewaveguide comprises a stack of waveguides.

10. The system of Example 9, wherein different waveguides of the stackof waveguides are configured to output light with different wavefrontdivergence as if projected from different distances from the user's eye.

11. The system of Example 9 or 10, wherein different waveguides of thestack of waveguides are configured to output light with differentcolors.

12. The system of any of Examples 9, 10, or 11, wherein differentwaveguides comprise first, second, and third waveguides, said system isconfigured such that the first is for red color light, the second for isgreen color light, and the third is for blue color light.

13. The system of any of the Examples above, wherein the in-couplingoptical element comprises a diffractive optical element or reflector.

14. The system of any of the Examples above, wherein the couplingoptical element comprises a diffractive optical element.

15. The system of any of the Examples above, wherein the out-couplingoptical element comprises a diffractive optical element.

16. The system of any of the Examples above, wherein the couplingelement is configured to increase a dimension of the eyebox along atleast one axis.

17. The system of Example 16, further comprising an orthogonal pupilexpander comprising at least one light redirecting element in or on saidat least one waveguide that is configured to increase a dimension of aneyebox along an axis that is orthogonal to the at least one axis.

18. The system of Example 17, wherein said at least one lightredirecting element comprises a diffractive optical element.

19. The system of any of the Examples above, wherein the same couplingelement (a) couples light from said environment into said at least onewaveguide to be received by said camera and (b) couples light from saidimage projector out from said at least one waveguide to said user's eye.

20. The system of any of the above Examples, further comprising areflective surface having optical power disposed to receive lightreflected from the user's eye that passes through said eyepiece and todirect said light back to said eyepiece.

21. The system of Example 20, wherein said at least one coupling elementis configured such that light from the user's eye that passes throughthe eyepiece and is reflected from the reflective surface back to theeyepiece is coupled into said waveguide and guided therein.

22. The system of any of Examples 20 to 21, wherein the camera isdisposed in an optical path with respect to said at least oneout-coupling optical element to receive at least a portion of the lightfrom the user's eye that is reflected from the reflective surface andcoupled into said waveguide via the coupling element and guided thereinand that is coupled out from said waveguide by said outcoupling couplingelement.

23. The system of any of Examples 20 to 22, wherein the reflectivesurface reflects infrared light but transmits visible light.

24. The system of any of Examples 20 to 23, wherein the reflectivesurface is curved.

25. The system of any of Examples 20 to 24, wherein the reflectivesurface is disposed on a curved optical element.

26. The system of any of Examples 20 to 25, wherein the reflectivesurface is disposed on a concave mirror.

27. The system of any of Examples 20 to 26, wherein the reflectivesurface has positive optical power in reflection and negligible opticalpower in transmission.

28. The system any of Examples 20 to 27, wherein the reflective surfaceis configured to collimated light from the user's eye.

29. The system of any of Examples 20 to 28, wherein the reflectivesurface is configured to collimate light from the retina of the user'seye.

30. The system of any of Examples 20 to 29, wherein the reflectivesurface is configured to collimate light from an anterior region of theuser's eye.

31. The system of any of Examples 20 to 30, wherein the reflectivesurface is configured to collimate light from the cornea of the user'seye.

32. The system of any of Examples 20 to 31, wherein the reflectivesurface is formed on a curved optical element having an infraredreflective coating on said reflective surface.

33. The system of Example 33, wherein the curved optical element hasnegligible power for light transmitted therethrough.

34. The system of Example 32 or 33, wherein the curved optical elementhas first and second curved surface on opposite sides of the curvedoptical element, said first and second curved surfaces having the samecurvature.

35. The system of any of the Examples above, further comprising aretarder disposed with respect to the reflective surface and thecoupling optical element so as to rotate the polarization of lightpassing through the eye piece and reflected from the reflective surfaceback to the eye piece and the coupling optical element.

36. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization selective turning element.

37. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization grating.

38. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn light guided within the at leastone waveguide out of the waveguide to the eye as collimated lightdirected to the eye of the user.

39. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn collimated light from thereflective surface into the at least one waveguide.

40. The system of any of the Examples above, wherein the at least oneout-coupling element comprises an off-axis reflector.

41. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization selective turning element.

42. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization grating.

43. The system of any of the Examples above, further comprising acircular polarizer.

44. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization selective turning element.

45. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization grating.

46. The system of any of the Examples above, wherein the in-couplingelement comprises an off-axis reflector.

47. The system of any of Examples 20 to 34, wherein the reflectivesurface comprises a liquid crystal reflector.

48. The system of any of Examples 20 to 34 or 47, wherein the reflectivesurface comprises a cholesteric liquid crystal reflective lens.

49. The system of any of the Examples above, wherein the same waveguide(a) guides light coupled from the user's eye into said at least onewaveguide to be received by said camera so as to capture an image of atleast a portion of the eye of the user, and (b) guides light coupledfrom said image projector such that light from said projector can bedirected to said user's eye such that said image from said imageprojector is in the vision field of said the user.

50. The system of any of the Examples above, wherein the same couplingelement (a) couples light from said user's eye into said at least onewaveguide to be received by said camera and (b) couples light from saidimage projector out from said at least one waveguide to said user's eye.

51. The system of any of the Examples above, further comprisingelectronics configured to cause the camera to capture a first image whenlight reflected from the reflective surface is blocked.

52. The system of Example 51, wherein said electronics is configured tocause the camera to capture a second image when light reflected from thereflective surface is not blocked.

53. The system of Example 52, wherein said electronics is configured touse the first image to modify the second image.

54. The system of Example 53, wherein said electronics is configured tosubtract from the second image based on the first image.

55. The system of any of the Examples above, wherein said system isconfigured to perform eye tracking based on said image of said eye.

56. The system of Example 55, wherein performing eye tracking based onsaid image of said eye comprises storing an image of the retina of saideye.

57. The system of any of any of the Examples above, wherein said systemis configured to:

-   -   store an image of the retina of said eye;    -   capture an image of a portion of said retina of said eye;    -   compare the stored image of said retina with the image of said        portion of said retina; and    -   determine a gaze of the user based on the comparison of the        stored image and image of the portion of the retina.

58. The system of Example 57, wherein determining a gaze of the usercomprises determining to which portion of the retina corresponds to theimage of said portion of the retina.

59. The system of any of Examples 57 to 58, wherein determining a gazeof the user comprises determining an orientation of the eye.

60. The system of any of the above Examples, further comprising a lightsource disposed so as to illuminate of the user's eye.

61. The system of Example 60, wherein said light source comprises one ormore infrared light sources configured to direct infrared light to theuser's eye.

62. The system of Examples 60 or 61, wherein said light source comprisesone or more infrared light emitting diodes (LEDs).

63. The system of any of Examples 60 to 62, wherein said light source ispulsed.

64. The system of any of the Examples above, further comprising anoff-axis reflector disposed to receive light from said light source andilluminate said eye with said light.

65. A head mounted imaging system configured to image at least a portionof an environment in front of a user wearing the head mounted imagingsystem, said head-mounted imaging system comprising:

-   -   a frame configured to be supported on a head of the user;    -   a camera; and    -   an eyepiece disposed on the frame, at least a portion of said        eyepiece being transparent and disposed at a location in front        of the user's eye when the user wears said head-mounted imaging        system such that said transparent portion transmits light from        the environment in front of the user to the user's eye to        provide a view of the environment in front of the user, said        eyepiece comprising:        -   (a) at least one waveguide;        -   (b) at least one coupling optical element configured such            that light from the environment in front of the user wearing            the head mounted imaging system is coupled into said            waveguide and guided therein; and        -   (c) at least one out-coupling element configured to couple            light within said waveguide out of said waveguide and direct            said light to said camera,    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light from the environment in front of        the user that is coupled into said waveguide via the coupling        element and guided therein and that is coupled out from said        waveguide by said outcoupling coupling element such that images        of said environment may be captured by said camera.

66. The system of Example 65, wherein said camera comprises a detectorarray and imaging optics.

67. The system of Example 66, wherein said imaging optics is configuredto focus collimated light onto said detector array.

68. The system of any of Examples 65 to 67, wherein said at least onewaveguide comprises material that is transparent to visible light havinga refractive index sufficient to guide light in said waveguide by totalinternal reflection.

69. The system of any of Examples 65 to 68, wherein said at least onewaveguide comprises a stack of waveguides.

70. The system of Example 69, wherein different waveguides of the stackof waveguides are configured to output light with different wavefrontdivergence as if projected from different distances from the user's eye.

71. The system of Example 69 or 70, wherein different waveguides of thestack of waveguides are configured to output light with differentcolors.

72. The system of any of Examples 69 to 71, wherein different waveguidescomprise first, second, and third waveguides, said system is configuredsuch that the first is for red color light, the second for is greencolor light, and the third is for blue color light.

73. The system of any of Examples 65 to 72, wherein the coupling opticalelement comprises a diffractive optical element.

74. The system of any of Examples 65 to 73, wherein the out-couplingoptical element comprises a diffractive optical element.

75. The system of any of Examples 65 to 74, wherein the coupling elementis configured to increase a dimension of the eyebox along at least oneaxis.

76. The system of Example 75, further comprising an orthogonal pupilexpander comprising at least one light redirecting element in or on saidat least one waveguide that is configured to increase a dimension of aneyebox along an axis that is orthogonal to the at least one axis.

77. The system of Example 76, wherein said at least one lightredirecting element comprises a diffractive optical element.

Example Section III

1. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user and to image at least a portion of the eye of the userwearing the head mounted display system, said head-mounted displaysystem comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project an image;    -   a camera;    -   an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        the environment in front of the user to the user's eye to        provide a view of the environment in front of the user, said        eyepiece comprising:        -   (a) at least one waveguide;        -   (b) at least one in-coupling optical element configured to            in-couple light from said image projector into said at least            one waveguide so as to guide light from said image projector            therein;        -   (c) at least one coupling optical element configured to            couple light from said image projector guided within said            waveguide out of said waveguide and direct said light to the            user's eye; and        -   (d) at least one out-coupling element configured to couple            said light guided within said waveguide out of said            waveguide and direct said light to said camera; and    -   a reflective surface having optical power disposed to receive        light reflected from the user's eye that passes through said        eyepiece and to direct said light back to said eyepiece;    -   wherein the image projector is disposed in an optical path with        respect to said at least one in-coupling optical element to        in-couple light from said image projector into said waveguide to        be guided therein such that said light is coupled out from said        waveguide by said at least one coupling element to said user's        eye such that said image from said projector is in the vision        field of said the user,    -   wherein said at least one coupling element is configured such        that light from the user's eye that passes through the eyepiece        and is reflected from the reflective surface back to the        eyepiece is coupled into said waveguide and guided therein, and    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light from the user's eye that is        reflected from the reflective surface and coupled into said        waveguide via the coupling element and guided therein and that        is coupled out from said waveguide by said outcoupling coupling        element.

2. The system of Example 1, further comprising a light source disposedso as to illuminate of the user's eye.

3. The system of Example 2, wherein said light source comprises one ormore infrared light sources configured to direct infrared light to theuser's eye.

4. The system of Examples 2 or 3, wherein said light source comprisesone or more infrared light emitting diodes (LEDs).

5. The system of any of Examples 2 to 4, wherein said light source ispulsed.

6. The system of any of the Examples above, further comprising anoff-axis reflector disposed to receive light from said light source andilluminate said eye with said light.

7. The system of any of the Examples above, wherein the reflectivesurface reflects infrared light but transmits visible light.

8. The system of any of the Examples above, wherein the reflectivesurface is curved.

9. The system of any of the Examples above, wherein the reflectivesurface is disposed on a curved optical element.

10. The system of any of the Examples above, wherein the reflectivesurface is disposed on a concave mirror.

11. The system of any of the Examples above, wherein the reflectivesurface has positive optical power in reflection and negligible opticalpower in transmission.

12. The system of any of the Examples above, wherein the reflectivesurface is configured to collimated light from the user's eye.

13. The system of any of the Examples above, wherein the reflectivesurface is configured to collimate light from the retina of the user'seye.

14. The system of any of the Examples above, wherein the reflectivesurface is configured to collimate light from an anterior region of theuser's eye.

15. The system of any of the Examples above, wherein the reflectivesurface is configured to collimate light from the cornea of the user'seye.

16. The system of any of the Examples above, wherein the reflectivesurface is formed on a curved optical element having an infraredreflective coating on said reflective surface.

17. The system of Example 9 or 16, wherein the curved optical elementhas negligible power for light transmitted therethrough.

18. The system of any of Examples 9 or 16 or 17, wherein the curvedoptical element has first and second curved surface on opposite sides ofthe curved optical element, said first and second curved surfaces havingthe same curvature.

19. The system of any of the Examples above, further comprising aretarder disposed with respect to the reflective surface and thecoupling optical element so as to rotate the polarization of lightpassing through the eye piece and reflected from the reflective surfaceback to the eye piece and the coupling optical element.

20. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization selective turning element.

21. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization grating.

22. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn light guided within the at leastone waveguide out of the waveguide to the eye as collimated lightdirected to the eye of the user.

23. The system of any of the Examples above, wherein the at least onecoupling element is configured to turn collimated light from thereflective surface into the at least one waveguide.

24. The system of any of the Examples above, wherein the at least oneout-coupling element comprises an off-axis reflector.

25. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization selective turning element.

26. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization grating.

27. The system of any of the Examples above, further comprising acircular polarizer.

28. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization selective turning element.

29. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization grating.

30. The system of any of the Examples above, wherein the in-couplingelement comprises an off-axis reflector.

31. The system of any of the Examples above, wherein the reflectivesurface comprises a liquid crystal reflector.

32. The system of any of the Examples above, wherein the reflectivesurface comprises a cholesteric liquid crystal reflective lens.

33. The system of any of the Examples above, wherein said imageprojector comprises a light source, a modulator, and projection optics.

34. The system of any of the Examples above, wherein the image projectorcomprises scanning optical fiber.

35. The system of any of the Examples above, wherein the modulatorcomprises a light modulator.

36. The system of Example 34, wherein the light modulator comprises aspatial light modulator.

37. The system of any of the Examples above, wherein said cameracomprises a detector array and imaging optics.

38. The system of Example 36, wherein said imaging optics is configuredto focus collimated light onto a detector array.

39. The system of any of the Examples above, wherein said at least onewaveguide comprises material transparent to visible light having arefractive index sufficient to guide light in said waveguide by totalinternal reflection.

40. The system of any of the Examples above, wherein said at least onewaveguide comprises a stack of waveguides.

41. The system of Example 40, wherein different waveguides of the stackof waveguides are configured to output light with different wavefrontdivergence as if projected from different distances from the user's eye.

42. The system of Example 40 or 41, wherein different waveguides of thestack of waveguides are configured to output light with differentcolors.

43. The system of any of Examples 40, 41, or 42, wherein differentwaveguides comprise first, second, and third waveguides, said system isconfigured such that said first is for red color light, the second foris green color light, and the third is for blue color light.

44. The system of any of the Examples above, wherein the in-couplingoptical element comprises a diffractive optical element or reflector.

45. The system of any of the Examples above, wherein the couplingoptical element comprises a diffractive optical element.

46. The system of any of the Examples above, wherein the out-couplingoptical element comprises a diffractive optical element.

47. The system of any of the Examples above, wherein the couplingelement is configured to increase dimensions of the eyebox along atleast one axis.

48. The system of Example 47, further comprising an orthogonal pupilexpander comprising at least one light redirecting element in or on saidat least one waveguide that is configured to increase a dimension of aneyebox along an axis that is orthogonal to the at least one axis.

49. The system of Example 48, wherein said at least one lightredirecting element comprises a diffractive optical element.

50. The system of any of the Examples above, wherein the same waveguide(a) guides light coupled from the user's eye into said at least onewaveguide to be received by said camera so as to capture an image of atleast a portion of the eye of the user, and (b) guides light coupledfrom said image projector such that light from said projector can bedirected to said user's eye such that said image from said imageprojector is in the vision field of said the user

51. The system of any of the Examples above, wherein the same couplingelement (a) couples light from said user's eye into said at least onewaveguide to be received by said camera and (b) couples light from saidimage projector out from said at least one waveguide to said user's eye.

52. The system of any of the Examples above, further comprisingelectronics configured to cause the camera to capture a first image whenlight reflected from the reflective surface is blocked.

53. The system of Example 52, wherein said electronics is configured tocause the camera to capture a second image when light reflected from thereflective surface is not blocked.

54. The system of Example 53, wherein said electronics is configured touse the first image to modify the second image.

55. The system of Example 54, wherein said electronics is configured tosubtract from the second image based on the first image.

56. The system of any of the Examples above, wherein said system isconfigured to perform eye tracking based on said image of said eye.

57. The system of Example 56, wherein performing eye tracking based onsaid image of said eye comprises storing an image of the retina of saideye.

58. The system of any of any of the Examples above, wherein said systemis configured to:

-   -   store an image of the retina of said eye;    -   capture an image of a portion of said retina of said eye;    -   compare the stored image of said retina with the image of said        portion of said retina; and    -   determine a gaze of the user based on the comparison of the        stored image and image of the portion of the retina.

59. The system of Example 58, wherein determining a gaze of the usercomprises determining to which portion of the retina corresponds to theimage of said portion of the retina.

60. The system of any of Examples 58 to 59, wherein determining a gazeof the user comprises determining an orientation of the eye.

61. The system of any of the above Examples, wherein said couplingelement is configured such that light from the environment in front ofthe user wearing the head mounted display is coupled into said waveguideand guided therein.

62. The system of any of the above Examples, wherein the camera isdisposed in an optical path with respect to said at least oneout-coupling optical element to receive at least a portion of the lightfrom the environment in front of the user that is coupled into saidwaveguide via the coupling element and guided therein and that iscoupled out from said waveguide by said outcoupling coupling elementsuch that images of said environment may be captured by said camera.

63. The system of any of the above Examples, wherein the same waveguide(a) guides light coupled from said environment into said waveguide to bereceived by said camera so as to capture an image of at least a portionof the environment in front of the user, and (b) guides light coupledfrom said projector such that light from said projector can be directedto said user's eye so that said image from said projector is in thevision field of said the user.

64. The system of any of the above Examples, wherein the same couplingelement (a) couples light from said environment into said at least onewaveguide to be received by said camera and (b) couples light from saidimage projector out from said at least one waveguide to said user's eye.

65. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user and to image at least a portion of the eye of the userwearing the head mounted display system, said head-mounted displaysystem comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project an image;    -   a camera;    -   an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user, said eyepiece        comprising:        -   (a) at least one waveguide;        -   (b) at least one in-coupling optical element configured to            in-couple light from said image projector into said at least            one waveguide so as to guide light from said image projector            therein;        -   (c) at least one coupling optical element configured to            couple light from said image projector guided within said            waveguide out of said waveguide and direct said light to the            user's eye; and        -   (d) at least one out-coupling element configured to couple            said light guided within said waveguide out of said            waveguide and direct said light to said camera; and    -   a positive lens having positive optical power disposed in an        optical path between the user's eye and said eyepiece such that        light reflected from the user's eye is transmitted through said        lens to said eyepiece; and    -   a negative lens having negative optical power disposed on the        other side of the eyepiece as the positive lens to offset the        power of said positive lens for light from the environment in        front of the user,    -   wherein the image projector is disposed in an optical path with        respect to said at least one in-coupling optical element to        couple light from said image projector into said waveguide to be        guided therein such that said light is coupled out from said        waveguide by said at least one coupling element to said user's        eye such that said image from said image projector is in the        vision field of said the user,    -   wherein said at least one coupling element is configured such        that light from the user's eye that passes through the lens to        the eyepiece is coupled into said waveguide and guided therein,        and    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light from the user's eye that is        reflected from the reflective surface and coupled into said        waveguide via the coupling element and guided therein and that        is coupled out from said waveguide by said out-coupling coupling        element.

66. The system of Example 65, wherein said positive lens comprises aFresnel lens.

67. The system of Example 65 or 66, wherein said positive lens isconfigured to collimate light from an anterior region of said user'seye.

68. The system of any of Examples 65, 66, or 67 above, wherein saidpositive lens is configured to collimate light from the cornea of saiduser's eye.

69. The system of any of Examples 65 to 68, wherein said system isconfigured to perform eye tracking based on said image of said eye.

70. The system of any of Examples 65 to 69, further comprising a lightsource disposed so as to illuminate of the user's eye.

71. The system of Example 70, wherein said light source comprises one ormore infrared light sources configured to direct infrared light to theuser's eye.

72. The system of Examples 70 or 71, wherein said light source comprisesone or more infrared light emitting diodes (LEDs).

73. The system of any of the Examples above, wherein said system isconfigured to identify the user via biometric sensing based on saidimage of said eye.

Example Section IV

1. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user, said head-mounted display system comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project images into the user's        eye to display image content in the vision field of the user;    -   at least one camera;    -   at least one waveguide;    -   at least one coupling optical element configured such that light        is coupled into said waveguide and guided therein, said at least        one coupling optical element comprising a diffractive optical        element having optical power; and    -   at least one out-coupling element configured to couple light        guided within said waveguide out of said waveguide and direct        said light to said camera,    -   wherein the camera is disposed in an optical path with respect        to said at least one out-coupling optical element to receive at        least a portion of the light that is coupled into said waveguide        via the coupling optical element and guided therein and that is        coupled out from said waveguide by said out-coupling coupling        element such that images may be captured by said camera.

2. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said at least one waveguide and guided therein such that images ofsaid eye may be captured by said at least one camera.

3. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected from ananterior portion of the eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of said eye may be captured by said camera such that said atleast one camera can capture images of said anterior portion of saideye.

4. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected from acorneal surface of said eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of said eye may be captured by said camera such that said atleast one camera can capture images of said corneal surface of said eye.

5. The system of any of the Examples above, wherein the optical power ofsaid coupling optical element is configured to increase collimation oflight reflected from the eye that is coupled into the waveguide to beguided to the camera.

6. The system of any of the Examples above, wherein the optical power ofsaid coupling optical element is configured to increase collimation oflight reflected from an anterior portion of the eye that is coupled intothe waveguide to be guided to the camera.

7. The system of any of the Examples above, wherein the optical power ofsaid coupling optical element is configured increase collimation oflight reflected from the cornea of the eye that is coupled into thewaveguide to be guided to the camera.

8. The system of any of Examples 1 or 7, wherein the optical powercomprises positive optical power.

9. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light reflected fromthe retina of the eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of said retina may be captured by said camera.

10. The system of any of the Examples above, further comprising aneyepiece disposed on the frame, said eyepiece configured to direct lightinto said user's eye to display augmented reality image content to theuser's vision field, at least a portion of said eyepiece beingtransparent and disposed at a location in front of the user's eye whenthe user wears said head-mounted display such that said transparentportion transmits light from an environment in front of the user to theuser's eye to provide a view of the environment in front of the user.

11. The system of Example 10, wherein said eyepiece is configured toreceive light from said image projector and to direct said light intosaid user's eye to display augmented reality image content to the user'svision field.

12. The system of any of Examples 10-11, wherein said eyepiece comprisessaid at least one waveguide.

13. The system of any of Examples 10-12, wherein said image projector isconfigured to direct light into an edge of said eyepiece.

14. The system of Examples 12 or 13, wherein said image projector isconfigured to direct light into an edge of said at least one waveguide.

15. The system of any of the Examples above, further comprising at leastone in-coupling optical element configured to in-couple light from saidimage projector into said at least one waveguide so as to guide lightfrom said image projector for providing said image content to saiduser's eye.

16. The system of any of Examples 1 to 15, further comprising at leastone image content out-coupling optical element configured to couplelight from said image projector guided within said waveguide out of saidat least one waveguide such that image content can be viewed by theuser's eye.

17. The system of any of the Examples above, wherein said at least onecoupling optical element faces the eye of the user wearing the headmounted imaging system to receive light from said eye.

18. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light from theenvironment in front of the user wearing the head mounted imaging systemis coupled into said at least one waveguide and guided therein such thatimages of said environment may be captured by said camera.

19. The system of any of the Examples above, wherein said at least onecoupling optical element faces the environment in front of the userwearing the head mounted imaging system to receive light from saidenvironment.

20. The system of Example 16, wherein said at least one coupling opticalelement is configured such that light is coupled into a first waveguideand guided therein to said camera and said at least one image contentout-coupling optical element is configured to couple light from saidimage projector guided within a second waveguide out of said secondwaveguide.

21. The system of any of the Examples above, wherein said at least onecoupling optical element is configured such that light is coupled into afirst waveguide and guided therein to said camera and said imageprojector is configured to couple light into a second waveguide toprovide image content to said eye.

22. The system of any of the Examples above, wherein said imageprojector comprises a light source, a modulator, and projection optics.

23. The system of any of the Examples above, wherein the image projectorcomprises scanning optical fiber.

24. The system of any of Examples 22, wherein the modulator comprises alight modulator.

25. The system of Example 24, wherein the light modulator comprises aspatial light modulator.

26. The system of any of the Examples above, wherein said cameracomprises a detector array and imaging optics.

27. The system of Example 26, wherein said imaging optics is configuredto focus collimated light onto said detector array.

28. The system of any of the Examples above, wherein said at least onewaveguide comprises material that is transparent to visible light havinga refractive index sufficient to guide light in said waveguide by totalinternal reflection.

29. The system of any of the Examples above, wherein said at least onewaveguide comprises material that is transparent to infrared lighthaving a refractive index sufficient to guide light in said waveguide bytotal internal reflection.

30. The system of any of the Examples above, wherein said at least onewaveguide comprises a stack of waveguides.

31. The system of Example 30, wherein different waveguides of the stackof waveguides are configured to output light with different wavefrontdivergence as if projected from different distances from the user's eye.

32. The system of Example 30 or 31, wherein different waveguides of thestack of waveguides are configured to output light with differentcolors.

33. The system of any of Examples 30, 31, or 32, wherein differentwaveguides comprise first, second, and third waveguides, said system isconfigured such that the first is for red color light, the second for isgreen color light, and the third is for blue color light.

34. The system of any of the Examples 15 to 33, wherein the at least onein-coupling optical element comprises a diffractive optical element.

35. The system of any of the Examples 15 to 33, wherein the at least onein-coupling optical element comprises a diffraction grating.

36. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization selective turning element.

37. The system of any of the Examples above, wherein the in-couplingelement comprises a polarization grating.

38. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization selective turning element.

39. The system of any of the Examples above, wherein the at least onecoupling element comprises a polarization grating.

40. The system of any of the Examples above, wherein the couplingoptical element comprises liquid crystal.

41. The system of any of the Examples above, wherein the couplingoptical element comprises a liquid crystal polarization grating.

42. The system of any of the Examples above, wherein the out-couplingoptical element comprises a diffractive optical element.

43. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization selective turning element.

44. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a polarization grating.

45. The system of any of the Examples above, wherein the at least oneout-coupling element comprises liquid crystal.

46. The system of any of the Examples above, wherein the at least oneout-coupling element comprises a liquid crystal polarization grating.

47. The system of any of the Examples above, wherein the at least oneout-coupling element comprises an off-axis reflector.

48. The system of any of the Examples above, wherein the same waveguide(a) guides light coupled from the user's eye into said at least onewaveguide to be received by said camera so as to capture an image of atleast a portion of the eye of the user, and (b) guides light coupledfrom said image projector such that light from said projector can bedirected to said user's eye such that said image from said imageprojector is in the vision field of said the user.

49. The system of any of the Examples above, wherein said system isconfigured to perform eye tracking based images of said eye.

50. The system of Example 49, wherein performing eye tracking based onsaid images of said eye comprises storing an image of the retina of saideye.

51. The system of any of any of the Examples above, wherein said systemis configured to:

-   -   obtain an image of a portion of said retina of said eye using        said camera;    -   compare one or more stored images of said retina with the image        of said portion of said retina; and    -   determine a gaze of the user based on the comparison of the one        or more stored images and the image of the portion of the retina        obtained from the camera.

52. The system of Example 51, wherein determining a gaze of the usercomprises determining to which portion of the retina corresponds to theimage of said portion of the retina.

53. The system of any of Examples 51 to 52, wherein determining a gazeof the user comprises determining an orientation of the eye.

54. The system of any of the Examples above, wherein said system isconfigured to obtain biometric data based on one or more images of theuser's eye obtained with said camera.

55. The system of any of the Examples above, wherein said system isconfigured to identify the user via biometric sensing based on one ormore images of said eye obtained with said camera.

56. The system of any of the above Examples, wherein said system isconfigured to provide illumination of a first polarization and topreferentially capture images with said camera using light of a secondpolarization different than said first polarization.

57. The system of any of the above Examples, wherein said system isconfigured to illuminate said user's eye with light of a firstpolarization and to preferentially capture images of said user's eyewith said camera using light of a second polarization different thansaid first polarization.

58. The system of Examples 60 or 61, wherein said first and secondpolarizations are orthogonal.

59. The system of any of the above Examples, further comprising a lightsource disposed so as to provide illumination so as to capture imageswith said camera.

60. The system of any of the above Examples, further comprising a lightsource disposed so as to illuminate of the user's eye.

61. The system of Examples 59 or 60, wherein said light source comprisesone or more infrared light sources.

62. The system of any of Examples 59 to 61, wherein said light sourcecomprises one or more infrared light emitting diodes (LEDs).

63. The system of any of Examples 59 to 63, wherein said light source ispulsed.

64. The system of any of Examples 59 to 63, wherein said light source isconfigured to input light into a waveguide to provide said illumination.

65. The system of any of Examples 59 to 64, wherein said light source isconfigured to input light into a waveguide disposed with respect to saideye to provide illumination to said eye.

66. The system of Examples 64 or 65, further comprising an illuminationin-coupling optical element configured to couple light from said lightsource into said waveguide.

67. The system of any of Examples 60 to 66, wherein said light source isconfigured to input light into said at least one waveguide to provideillumination.

68. The system of any of Examples 59 to 68, wherein said light source isconfigured to input light into the same waveguide as used to projectimage content to the user's eye.

69. The system of any of Examples 59 to 69, wherein said light source isconfigured, to provide illumination to the user's eye, to input lightinto the same waveguide as used to guide light to the camera.

70. The system of any of Examples 59 to 70, wherein said light source isconfigured to input light into the same waveguide as used to guide lightfrom the user's eye to the camera.

71. The system of any of Examples 64 to 70, further comprising anillumination in-coupling optical element configured to couple light fromsaid light source into said waveguide to provide illumination.

72. The system of Example 71, wherein said illumination in-couplingoptical element is polarization selective, in-coupling light of a firstpolarization.

73. The system of Example 59 to 77, wherein said light source is apolarized light source configured to output polarized light having afirst polarization.

74. The system of any of Examples 59 to 78, wherein said light source isconfigured to direct polarized light having a first polarization ontosaid eye.

75. The system of Example 59 to 79, further comprising an illuminationpolarizer having a first polarization disposed in the optical pathbetween said light source and said eye to polarize light directed tosaid eye.

76. The system of Example 75, wherein the illumination polarizer isdisposed in the optical path between said light source and saidwaveguide configured to provide illumination.

77. The system of any of Examples 59 to 76, further comprising an imageacquisition polarizer in an optical path between said eye and saidcamera.

78. The system of Example 77, wherein said image acquisition polarizeris proximal said camera.

79. The system of Examples 77 or 78, wherein said image acquisitionpolarizer is disposed in an optical path between (a) said at least onewaveguide configured guide light to said camera and (b) said camera.

80. The system of any of Examples 77 to 79, wherein said imageacquisition polarizer reduces the amount of light of said firstpolarization that reaches said camera.

81. The system of Examples 77 to 80, wherein said image acquisitionpolarizer comprises a polarizer configured to selectively coupling lightof a second polarization different than said first polarization to saidcamera.

82. The system of any of the Examples above, further comprising at leastone light consolidating element disposed in an optical path between saidat least one coupling element and said at least one out-coupling opticalelement to reduce lateral spatial extent of light from said at least onecoupling element prior to reaching said at least one out-couplingoptical element.

83. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a diffractive optical element.

84. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a hologram or diffraction grating.

85. The system of any of Examples 51, wherein the one or more storedimages of the retina of the eye comprise a composite image of the retinaof the eye generated using a plurality of images of different portionsof the retina of the eye.

86. The system of any of Examples 51 to 85, wherein the composite imageof the retina comprises a plurality of images of the retina stitchedtogether.

87. The system of any of Examples 51 to 86, wherein the plurality ofimages of the retina stitched together comprises images obtained when afixation target was displayed in the vision field of the user at variouslocations, respectively.

88. The system of any of Examples 51 to 87, wherein the one or morestored images of the retina comprises images obtained when a fixationtarget was displayed in the vision field of the user at variouslocations, respectively.

89. The system of any of Examples 51 to 88, wherein the system isfurther configured to use the obtained image of the portion of theretina of the eye to update the composite image.

90. The system of any of Examples 51 to 89, wherein using the obtainedimage of the portion of the retina to update the composite image of theretina comprises stitching the obtained image into a section of thecomposite image corresponding to the portion of the retina shown in theobtained image.

91. The system of any of Examples 51 to 90, wherein the system isfurther configured to apply a digital filter to the obtained image ofthe portion of the retina of the eye to obtain a filtered image of theportion of the retina.

92. The system of Examples 91, wherein the system is further configuredto compare one or more stored images of the retina with the filteredimage of the portion of the retina.

93. The system of any of Examples 91 to 92, wherein the digital filtercomprises a Frangi Filter.

94. The system of any of Examples 51 to 93, wherein the system isconfigured to apply edge enhance the obtained image of the portion ofthe retina.

95. The system of any of the Examples above, wherein said system isconfigured to perform user identification verification using images ofthe retina.

96. The system of any of the Examples above, wherein said system isconfigured to:

-   -   obtain an image of a portion of said retina of said eye using        said camera;    -   compare one or more stored images of said retina with the image        of said portion of said retina.

97. The system of Example 96, wherein the one or more stored images ofthe retina of the eye comprise a composite image of the retina of theeye generated using a plurality of images of different portions of theretina of the eye.

98. The system of any of Examples 96 to 97, wherein the composite imageof the retina comprises a plurality of images of the retina stitchedtogether.

99. The system of any of Examples 96 to 98, wherein the plurality ofimages of the retina stitched together comprises images obtained when afixation target was displayed in the vision field of the user at variouslocations, respectively.

100. The system of any of Examples 96 to 99, wherein the one or morestored images of the retina comprises images obtained when a fixationtarget was displayed in the vision field of the user at variouslocations, respectively.

101. The system of any of Examples 96 to 100, wherein the system isfurther configured to use the obtained image of the portion of theretina of the eye to update the composite image.

102. The system of any of Examples 96 to 101, wherein using the obtainedimage of the portion of the retina to update the composite image of theretina comprises stitching the obtained image into a section of thecomposite image corresponding to the portion of the retina shown in theobtained image.

103. The system of any of Examples 96 to 102, wherein the system isfurther configured to apply a digital filter to the obtained image ofthe portion of the retina of the eye to obtain a filtered image of theportion of the retina.

104. The system of Examples 103, wherein the system is furtherconfigured to compare one or more stored images of the retina with thefiltered image of the portion of the retina.

105. The system of any of Examples 96 to 104, wherein the digital filtercomprises a Frangi Filter.

106. The system of any of Examples 96 to 105, wherein the system isconfigured to apply edge enhancement the obtained image of the portionof the retina.

107. The system of any of Examples above, wherein the optical powercorresponds to a focal length about the distance of the eye to thecoupling optical element.

108. The system of any of Examples above, wherein the optical powercorresponds to a focal length of between 15 mm and 25 mm.

109. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user, said head-mounted display system comprising:

-   -   a frame configured to be supported on a head of the user;    -   at least one waveguide,    -   an image projector for projecting images into the user's eye to        display image content in the vision field of the user, said        image projector configured to input light into at least one of        said at least one waveguide to be guided therein;    -   at least one image content out-coupling optical element        configured to couple light from said image projector guided        within said at least one of said at least one waveguide out        thereof such that image content can be viewed by the user's eye.    -   a camera;    -   at least one coupling optical element configured such that light        is coupled into at least one of said at least one waveguide and        guided therein to said camera; and    -   at least one out-coupling element configured to couple light        guided within said at least one of said at least one waveguide        out thereof and direct said light to said camera, said camera        disposed in an optical path with respect to said at least one        out-coupling optical element to receive at least a portion of        the light that is coupled into said at least one of said at        least one waveguide via the coupling optical element and guided        therein and that is coupled out from said at least one of said        at least one waveguide by said out-coupling coupling element        such that images may be captured by said camera,    -   wherein said at least one image content out-coupling optical        element and said at least one coupling optical element are        disposed laterally with respect to each other.

110. The system of any of Example 109, wherein said at least one imagecontent out-coupling optical element is disposed more nasally than saidat least one out-coupling element.

111. The system of any of Example 110, wherein said at least one imagecontent out-coupling optical element is disposed more temporally thansaid at least one out-coupling element.

112. The system of any of the Examples above, further comprising atleast one light consolidating element disposed in an optical pathbetween said at least one coupling element and said at least oneout-coupling optical element to reduce lateral spatial extent of lightfrom said at least one coupling element prior to reaching said at leastone out-coupling optical element.

113. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a diffractive optical element.

114. The system of any of the Examples above, wherein said at least onelight consolidating element comprises a hologram or diffraction grating.

115. The system of any of the Examples above, wherein said couplingoptical element comprises a diffractive optical element having opticalpower.

116. The system of any of the Examples above, further comprising a lensdisposed with respect to said coupling optical element to provideoptical power to light received by said coupling optical element.

117. The system of any of the Examples above, wherein the optical poweris configured to increase collimation of light reflected from the eyethat is coupled into the waveguide to be guided to the camera.

118. The system of any of the Examples above, wherein the optical poweris configured to increase collimation of light reflected from ananterior portion of the eye that is coupled into the waveguide to beguided to the camera.

119. The system of any of the Examples above, wherein the optical poweris configured increase collimation of light reflected from the cornea ofthe eye that is coupled into the waveguide to be guided to the camera.

120. The system of any of Examples above, wherein the optical powercomprises positive optical power.

121. The system of any of Examples above, wherein the optical powercorresponds to a focal length about the distance of the eye to thecoupling optical element.

122. The system of any of Examples above, wherein the optical powercorresponds to a focal length of between 15 mm and 25 mm.

123. The system of any of the Examples above, wherein said couplingoptical element is configured such that light reflected from the eye ofthe user wearing the head mounted display system is coupled into saidwaveguide and guided therein such that images of said eye may becaptured by said camera, said system configured to image an anteriorportion of said eye.

124. The system of any of the Examples above, wherein said couplingoptical element is configured such that light reflected from the eye ofthe user wearing the head mounted display system is coupled into saidwaveguide and guided therein such that images of said eye may becaptured by said camera, said system configured to image a cornealsurface of said eye.

125. The system of any of the Examples above, wherein said secondcoupling optical element is configured such that light reflected fromthe eye of the user wearing the head mounted display system is coupledinto said waveguide and guided therein such that images of said eye maybe captured by said camera, said system configured to image the retinaof said user's eye.

126. The system of any of the above Examples, wherein said system isconfigured to provide illumination of a first polarization and topreferentially capture images with said camera using light of a secondpolarization different than said first polarization.

127. The system of any of the above Examples, wherein said system isconfigured to illuminate said user's eye with light of a firstpolarization and to preferentially capture images of said user's eyewith said camera using light of a second polarization different thansaid first polarization.

128. The system of Examples 126 or 127, wherein said first and secondpolarizations are orthogonal.

129. The system of any of Examples 126 to 128, further comprising anillumination in-coupling optical element configured to couple light froma light source into said waveguide to provide illumination.

130. The system of Example 129, wherein said illumination in-couplingoptical element is polarization selective, in-coupling light of a firstpolarization.

131. The system of any of the Examples above, further comprising a lightsource that is a polarized light source configured to output polarizedlight having a first polarization.

132. The system of any of Example above, wherein said light source isconfigured to direct polarized light having a first polarization ontosaid eye.

133. The system of any of the Examples above, further comprising anillumination polarizer having a first polarization disposed in theoptical path between said light source and said eye to polarize lightdirected to said eye.

134. The system of Example 133, wherein the illumination polarizer isdisposed in the optical path between said light source and saidwaveguide configured to provide illumination.

135. The system of any of the Example above, further comprising an imageacquisition polarizer in an optical path between said eye and saidcamera.

136. The system of Example 135, wherein said image acquisition polarizeris proximal said camera.

137. The system of Examples 135 or 136, wherein said image acquisitionpolarizer is disposed in an optical path between (a) said at least onewaveguide configured guide light to said camera and (b) said camera.

138. The system of any of Examples 135 to 137, wherein said imageacquisition polarizer reduces the amount of light of said firstpolarization that reaches said camera.

139. The system of Examples 135 to 138, wherein said image acquisitionpolarizer comprises a polarizer configured to selectively coupling lightof a second polarization different than said first polarization to saidcamera.

140. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user, said head-mounted display system comprising:

-   -   a frame configured to be supported on a head of the user;    -   an image projector configured to project images into the user's        eye to display image content in the vision field of the user;    -   at least one camera;    -   at least one waveguide;    -   a first coupling optical element configured such that light is        coupled into said at least one waveguide and guided therein to        at least one of said at least one cameras;    -   a second coupling optical element configured such that light is        coupled into said at least one waveguide and guided therein to        at least one of said at least one cameras; and    -   at least one out-coupling element configured to couple light        coupled into said at least one waveguide by said first and        second coupling optical elements and guided within said at least        one waveguide out of said at least one waveguide and direct said        light to said at least one said camera,    -   wherein first coupling optical element and said second coupling        optical element are disposed laterally with respect to each        other.

141. The system of any of Example 140, wherein said first couplingoptical element comprising a diffractive optical element having opticalpower.

142. The system of any of the Examples above, further comprising a lensdisposed with respect to said first coupling optical element to provideoptical power to light received by said first coupling optical element.

143. The system of any of the Examples above, wherein said optical poweris configured to increase collimation of light reflected from the eyethat is coupled into the waveguide to be guided to the camera.

144. The system of any of the Examples above, wherein said optical poweris configured to increase collimation of light reflected from ananterior portion of the eye that is coupled into the waveguide to beguided to the camera.

145. The system of any of the Examples above, wherein said optical poweris configured increase collimation of light reflected from the cornea ofthe eye that is coupled into the waveguide to be guided to the camera.

146. The system of any of the Examples above, wherein the optical powercomprises positive optical power.

147. The system of any of the Examples above, wherein the optical powercorresponds to a focal length about the distance of the eye to firstcoupling optical element.

148. The system of any of any the Examples above, wherein the opticalpower corresponds to a focal length of between 15 mm and 25 mm.

149. The system of any of the Examples above, wherein said firstcoupling optical element is configured such that light reflected from ananterior portion of the eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of said anterior portion of said eye may be captured by saidcamera.

150. The system of any of the Examples above, wherein said firstcoupling optical element is configured such that light reflected from acorneal surface of the eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of the corneal surface said eye may be captured by said camera.

151. The system of any of the Examples above, wherein said secondcoupling optical element is configured such that light reflected fromthe retina of the eye of the user wearing the head mounted displaysystem is coupled into said waveguide and guided therein such thatimages of the retina of said eye may be captured by said camera.

152. The system of any of the Examples above, wherein said secondcoupling optical element does not include optical power.

153. The system of any of the Examples above, wherein said secondcoupling optical element does not include a lens in an optical pathbetween the eye and said second coupling optical element.

154. The system of any of the Examples above, wherein said first andsecond coupling optical elements couple light into said waveguide thatis guided therein to a single camera.

155. The system of any of the Examples above, wherein said at least onecamera comprises first and second cameras, said first coupling opticalelement configured to couples light into said waveguide that is guidedtherein to said first camera and said second coupling optical elementconfigured to couple light into said waveguide that is guided therein tothe second camera.

156. The system of any of the Examples above, wherein said at least onecamera comprises a single cameras, said first and second couplingoptical element configured to couple light into said waveguide that isguided therein to said single camera.

157. The system of any of the Examples above, wherein at least oneout-coupling element comprises a first out-coupling element forout-coupling light that is input into said at least one waveguidethrough said first coupling optical element and a second out-couplingelement for out-coupling light guided that is input into said at leastone waveguide through said second coupling optical element.

158. The system of any of the above Examples, wherein said system isconfigured to provide illumination of a first polarization.

159. The system of Example 158, said system is configured such thatlight received by said second coupling optical element is preferentiallyused to captures images with light having a second polarizationdifferent than said first polarization.

160. The system of any of the above Examples, wherein said system isconfigured to illuminate said user's eye with light of a firstpolarization.

161. The system of Example 160, wherein said system is configured suchthat light received by said second coupling optical element ispreferentially used to captures images of said eye with light having asecond polarization different than said first polarization.

162. The system of any of Examples 158 to 161, wherein said system isconfigured such that light received by said first coupling opticalelement enables capture of images of said eye with light having eithersaid first or second polarizations.

163. The system of any of Examples 158 to 162, wherein said first andsecond polarizations are orthogonal.

164. The system of any of Examples 158 to 163, further comprising anillumination in-coupling optical element configured to couple light froma light source into said waveguide to provide illumination.

165. The system of Example 164, wherein said illumination in-couplingoptical element is polarization selective, in-coupling light of a firstpolarization.

166. The system of any of Examples 158 to 165, further comprising alight source that is a polarized light source configured to outputpolarized light having a first polarization.

167. The system of any of Examples 158 to 166, wherein said light sourceis configured to direct polarized light having a first polarization ontosaid eye.

168. The system of any of Examples 158 to 167, further comprising anillumination polarizer having a first polarization disposed in theoptical path between said light source and said eye to polarize lightdirected to said eye.

169. The system of Example 168, wherein the illumination polarizer isdisposed in the optical path between said light source and saidwaveguide configured to provide illumination.

170. The system of any of Examples 158 to 169, further comprising animage acquisition polarizer in an optical path between said eye and saidcamera.

171. The system of any of Examples 158 to 169, wherein said imageacquisition polarizer is disposed in an optical path between said secondcoupling optical element and said at least one camera that receiveslight from said second coupling optical element.

172. The system of any of the Examples above, wherein at least oneout-coupling element comprises a first out-coupling element forout-coupling light that is input into said at least one waveguidethrough said first coupling optical element and a second out-couplingelement for out-coupling light guided that is input into said at leastone waveguide through said second coupling optical element.

173. The system of any of Examples 158 to 169, wherein said imageacquisition polarizer is disposed in an optical path between a secondout-coupling coupling optical element and said camera.

174. The system of Example 170, wherein said image acquisition polarizeris proximal said camera.

175. The system of Examples 170 or 171, wherein said image acquisitionpolarizer is disposed in an optical path between (a) said at least onewaveguide configured guide light to said camera and (b) said camera.

176. The system of any of Examples 170 to 172, wherein said imageacquisition polarizer reduces the amount of light of said firstpolarization that reaches said camera.

177. The system of Examples 170 to 173, wherein said image acquisitionpolarizer comprises a polarizer configured to selectively coupling lightof a second polarization different than said first polarization to saidcamera.

178. The system of any of Examples 158 to 169, wherein said secondout-coupling optical element is polarization selective, selectivelyoutcoupling light of said second polarization from said at least onewaveguide.

179. The system of any of the Examples above, wherein no polarizationselective optical elements that selectively direct said secondpolarization in comparison to said first polarization to said at leastone camera are not included in the path between the first couplingoptical element and said at least one camera receiving light therefrom.

180. The system of any of the Examples above, wherein said firstcoupling optical element is not a polarization selective coupler thatselectively couples said second polarization in comparison to said firstpolarization into said at least one waveguide.

181. The system of any of the Examples above, wherein the firstout-coupling optical element polarization is not a selective couplingoptical elements that selectively couples said second polarization incomparison to said first polarization to said at least one camera.

182. The system of any of the Examples above, wherein no polarizationselective optical elements that selectively direct said secondpolarization in comparison to said first polarization to said at leastone camera are included in the path between the first out-couplingoptical element and said at least one camera receiving light therefrom.

183. The system of any of the Examples above, wherein no polarizationselective optical elements that selectively direct said secondpolarization in comparison to said first polarization to said at leastone camera are included in the path between the first coupling opticalelement and said first out-coupling optical element.

184. The system of any of the Examples above, wherein and an opticalelement having optical power is disposed with respect to said firstcoupling optical element such that propagation of light coupled intosaid first coupling optical element is altered by said optical power orsaid first coupling optical element has optical power.

185. The system of any of Examples above, wherein an optical elementhaving optical power is disposed in an optical path to said firstcoupling optical element such that light coupled into said waveguidepasses through said optical element having optical power or said firstcoupling optical element has optical power.

186. The system of any of Examples above, wherein an optical elementhaving optical power is disposed in an optical path from said eye tosaid first coupling optical element such that light from said eyecoupled into said waveguide passes through said optical element havingoptical power or said first coupling optical element has optical power.

187. The system of any of the Examples above, wherein an optical elementhaving optical power is not disposed in an optical path from the eye tosaid second coupling optical element.

188. The system of any of the Examples above, wherein an optical elementhaving optical power is not disposed with respect to said secondcoupling optical element such that the propagation of light to saidsecond coupling optical element is not altered by an optical elementhaving optical power.

189. The system of any of Examples above, wherein said second couplingoptical element does not have optical power.

190. The system of any of the Examples above, wherein said system isconfigured such that said light from said first coupling element formsan image of an anterior surface of the eye on said at least one camerathereby enabling images of said anterior surface to be captured.

191. The system of any of the Examples above, wherein said system isconfigured such that said light from said first coupling optical elementforms an image of glint on said at least one camera thereby enablingimages of said glint to be captured.

192. The system of any of the Examples above, wherein said system isconfigured such that said light from said second coupling opticalelement forms an image of the retina on said at least one camera therebyenabling images of said retina to be captured.

193. The system of any of the Examples above, wherein said system isconfigured such that light from said first coupling optical elementpreferentially enabling images of glint to be captured by said at leastone camera and light from said second coupling optical elementpreferentially enables images of the retina to be captured by said atleast one camera.

194. The system of any of the Examples above, wherein said system isconfigured such that light from said first coupling optical elementpreferentially enabling images of an anterior surface of the eye to becaptured by said at least one camera and light from said second couplingoptical element preferentially enables images of the retina to becaptured by said at least one camera.

195. The system of any of the Examples above, wherein said system isconfigured such that light from said first coupling optical elementpreferentially enabling images of a corneal surface to be captured bysaid at least one camera and light from said second coupling opticalelement preferentially enables images of the retina to be captured bysaid at least one camera.

196. The system of any of the Examples above, wherein said first andsecond coupling optical elements are in contact with each other.

What is claimed is:
 1. A head mounted display system configured toproject light to an eye of a user to display augmented reality imagecontent in a vision field of said user, said head-mounted display systemcomprising: a frame configured to be supported on a head of the user; animage projector configured to project images into the user's eye todisplay image content in the vision field of the user; at least onecamera; at least one waveguide having a user side facing the user; atleast one coupling optical element configured to couple light from theeye of the user into said waveguide, said at least one coupling opticalelement comprising a diffractive optical element (i) having opticalpower, (ii) configured to couple light from the eye of the user directlyinto guided light in said waveguide, and (iii) disposed on the user sideof the waveguide; and at least one out-coupling element configured tocouple the guided light in said waveguide out of said waveguide anddirect said light to said camera, wherein said guided light propagatesfrom the optical coupling element to the out-coupling element entirelyby total internal reflection within said waveguide, wherein the camerais disposed in an optical path with respect to said at least oneout-coupling optical element to receive at least a portion of the lightthat is coupled into said waveguide via the coupling optical element andguided therein and that is coupled out from said waveguide by saidout-coupling coupling element such that images may be captured by saidcamera.
 2. The system of claim 1, wherein said at least one couplingoptical element is configured such that light reflected from the eye ofthe user wearing the head mounted display system is coupled into said atleast one waveguide and guided therein such that images of said eye maybe captured by said at least one camera.
 3. The system of claim 1,wherein said at least one coupling optical element is configured suchthat light reflected from an anterior portion of the eye of the userwearing the head mounted display system is coupled into said waveguideand guided therein such that images of said eye may be captured by saidcamera such that said at least one camera can capture images of saidanterior portion of said eye.
 4. The system of claim 1, wherein said atleast one coupling optical element is configured such that lightreflected from a corneal surface of said eye of the user wearing thehead mounted display system is coupled into said waveguide and guidedtherein such that images of said eye may be captured by said camera suchthat said at least one camera can capture images of said corneal surfaceof said eye.
 5. The system of claim 1, wherein the optical power of saidcoupling optical element is configured to increase collimation of lightreflected from the eye that is coupled into the waveguide to be guidedto the camera.
 6. The system of claim 1, wherein the optical power ofsaid coupling optical element is configured to increase collimation oflight reflected from an anterior portion of the eye that is coupled intothe waveguide to be guided to the camera.
 7. The system of claim 1,wherein the optical power of said coupling optical element is configuredto increase collimation of light reflected from the cornea of the eyethat is coupled into the waveguide to be guided to the camera.
 8. Thesystem of claim 1, wherein the optical power comprises positive opticalpower.
 9. The system of claim 1, further comprising an eyepiece disposedon the frame, said eyepiece configured to direct light into said user'seye to display augmented reality image content to the user's visionfield, at least a portion of said eyepiece being transparent anddisposed at a location in front of the user's eye when the user wearssaid head-mounted display such that said transparent portion transmitslight from an environment in front of the user to the user's eye toprovide a view of the environment in front of the user.
 10. The systemof claim 9, wherein said eyepiece is configured to receive light fromsaid image projector and to direct said light into said user's eye todisplay augmented reality image content to the user's vision field. 11.The system of claim 9, wherein said eyepiece comprises said at least onewaveguide.
 12. The system of claim 9, wherein said image projector isconfigured to direct light into an edge of said eyepiece.
 13. The systemof claim 1, further comprising at least one in-coupling optical elementconfigured to in-couple light from said image projector into said atleast one waveguide so as to guide light from said image projector forproviding said image content to said user's eye.
 14. The system of claim1, further comprising at least one image content out-coupling opticalelement configured to couple light from said image projector guidedwithin said waveguide out of said at least one waveguide such that imagecontent can be viewed by the user's eye.
 15. The system of claim 14,wherein said at least one coupling optical element is configured suchthat light is coupled into a first waveguide and guided therein to saidcamera, and said at least one image content out-coupling optical elementis configured to couple light from said image projector guided within asecond waveguide out of said second waveguide.
 16. The system of claim1, wherein said at least one coupling optical element faces the eye ofthe user wearing the head mounted imaging system to receive light fromsaid eye.
 17. The system of claim 1, wherein said at least one couplingoptical element is configured such that light from the environment infront of the user wearing the head mounted imaging system is coupledinto said at least one waveguide and guided therein such that images ofsaid environment may be captured by said camera.
 18. The system of claim1, wherein said at least one coupling optical element faces theenvironment in front of the user wearing the head mounted imaging systemto receive light from said environment.
 19. The system of claim 1,wherein said at least one coupling optical element is configured suchthat light is coupled into a first waveguide and guided therein to saidcamera, and said image projector is configured to couple light into asecond waveguide to provide image content to said eye.
 20. The system ofclaim 1, wherein the head mounted display system is further configuredto image light from a world side of the head mounted display to thecamera.
 21. The system of claim 1, wherein both the at least onecoupling optical element and said out-coupling element are located onthe user side of said waveguide.